Fetal immune response following prematurely ruptured membranes

Concentrations of immunoglobulins (Ig)A1, and IgA2, IgD, IgE, IgG, and IgM have been determined in cord blood, amniotic fluid, and maternal serum in a group of patients with a history of prematurely ruptured membranes (PRM) prior to the onset of labor and in a control group of patients undergoing normal delivery and without a history of infection during pregnancy. IgA and IgD were determined by sensitive hemagglutination-inhibition tests; IgG and IgM, by radial immunodiffusion; IgE, by a radioimmunoassay. There was evidence for an immune response in 10 of 16 cases of PRM: five of 16 had increased IgA but normal IgM; three of 16 had increased IgA and IgM; two of 16 had high IgM and normal IgA in cord blood. In patients with significantly increased levels of either IgA or IgM or both, there was a decreased level of IgD. These changes are most likely the result of the immune response to ascending infection from the maternal genitals. The sensitive testing method employed could demonstrate the presence of IgD in 53 per cent of normal cord blood samples and 72 per cent of amniotic fluid samples obtained at term. IgE was found in all normal cord blood and amniotic fluid samples tested. By concentrating the amniotic fluid up to 180-fold, IgM was demonstrated in all normal samples tested. The potential importance of IgA determinations in cord blood in addition to IgM determination for detection of intrauterine infections is stressed.     

Monoclonal and polyclonal antibodies to chicken immunoglobulin isotypes specifically detect turkey immunoglobulin isotypes

Turkey immunoglobulin (Ig) isotypes IgG and IgM were isolated from blood and IgA was isolated from bile. Isolation was accomplished by gel filtration of the ammonium sulphate cut on Sephacryl S-200. Using immunoelectrophoresis and indirect ELISA, the cross-reactivity between antibodies, of monoclonal and polyclonal origin, specific for the Ig isotypes of chicken, and the purified turkey Ig isotypes was evaluated. Commercially available polyclonal antibodies, anti-chicken/IgA (alpha-chain specific, affinity purified), anti-chicken/IgG (Fc-fragment specific) and anti-chicken/IgM (mu-chain specific) showed an interspecies cross-reactivity with the corresponding turkey Ig isotypes. The monoclonal antibody (MAb) AV-G3 specifically detected turkey IgG, whereas MAb M1 reacted exclusively with turkey IgM. This panel of anti-immunoglobulins represents a useful tool for examining the humoral immune responses of turkeys.     

Humoral immune response against antigen 60 in BCG-vaccinated infants

An ELISA assay based on the A-60 antigen complex from Mycobacterium bovis BCG cytoplasm was used to detect anti-mycobacterial antibodies of different classes in the sera of 63 BCG-vaccinated infants during the 6-month post-vaccination period. The mean IgM and IgA levels increased, whereas the mean IgG level decreased after BCG vaccination. However, in a minority of cases only Ig levels were above the cut-off line: this was true for IgM in 11/63 (17%) cases and for IgA in 14/63 (22%) of cases but none of the tested infants was anti-A60 IgG ELISA positive. Fifty-two infants (83%) were tuberculin-positive eight weeks after vaccination, and no significant difference in mean antibody levels of tuberculin-positive and negative cases was observed, except for IgG (p < 0.05).     

Immunoglobulin class and subclass distribution of antibodies reactive with the immunodominant antigen of Actinobacillus actinomycetemcomitans serotype b

The aims of this study were to determine the immunodominant antigens of Actinobacillus actinomycetemcomitans serotype b (Aab) for the different immunoglobulin (Ig) classes and subclasses and to determine the relative levels of these different Igs in serum. Seropositive early-onset periodontitis patients were sampled, and the Ig classes IgG, IgA, and IgM and subclasses IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2 were studied. Reactivity with Aab antigens was assessed by using the Western blot (immunoblot) in limiting dilution analysis and radioimmunoassay with sera from 13 early-onset periodontitis subjects. A smeared antigen in the upper portion of the immunoblots, typical of high-molecular-weight LPS, was immunodominant for IgG, IgA, IgM, IgG1, IgG2, IgG3, IgA1, and IgA2. This smeared antigen was present in every patient for all of these Igs at the endpoint. A few additional antigens were also present at the endpoint in some patients, but none were present in more than half of the subjects. The distribution of antibody titers by Ig classes reactive with the Aab immunodominant antigen was IgG > IgA > IgM. The distribution of antibody titers by IgG subclass was IgG2 > IgG1 approximately IgG3. Further quantitation by radioimmunoassay revealed that the mean concentration of IgG2 (65.7 micrograms/ml) was significantly greater than that of IgG1 (8.8 micrograms/ml). The IgA subclass distribution was IgA1 > IgA2, with IgA1 apparently being second only to IgG2. Therefore, the Aab antigen eliciting the highest antibody level in virtually all Ig classes and subclasses appeared to be lipopolysaccharide, and IgG2 was markedly elevated over all other serum Ig classes or subclasses reactive with Aab.     

Effect of fetal thymectomy on IgG, IgM, and IgA concentrations in sheep

Serum concentrations of immunoglobulins (Ig) IgG, IgG, IgM, and IgA were compared for normal and thymectomized lambs. Fetal thymectomies were performed in utero from 55 to 67 days of gestation. High serum IgG, IgM, and IgA concentrations occurred in all lambs after they ingested colostrum; however, the concentration of these Ig, as measured by single radial immunodiffusion, decreased exponentially during the first 16 days after birth. The half-life values for IgG, IgM, and IgA during this period in both normal and thymectomized lambs were about 25, 6, and 2 days, respectively. Increasing amounts of IgG were not detected in the serums of either group until 1 month of age. At 64 to 128 days, significantly smaller quantities of IgG and IgG were found in thymectomized lambs, whereas concentrations of IgA and IgM were similar in both groups. The results indicate that the thymus may regulate production of IgG in sheep.     

Polyclonal immunoglobulin response of thymic, hepatic and splenic lymphocytes from fetal, germ-free and conventionally reared pigs to different B-cell activators

Immunoglobulin (Ig) response to different polyclonal B-cell activators was measured by ELISA in cell culture media of thymocytes, splenocytes and liver cells isolated from pig fetuses, 8-d-old germ-free piglets and conventionally reared pigs. Both in fetal and in postnatal life polyclonally stimulated lymphocytes were found to produce predominantly the IgM isotype; the first IgM formation was detected in 50-d-old fetal liver (gestation in pigs lasts 114 d). Surprisingly, 73-d-old fetal thymic cells were shown to be induced to Ig synthesis and secretion. In contrast to splenocytes of the same age, which secreted exclusively IgM, fetal thymocytes produced IgM, IgG and IgA. Polyclonally stimulated splenic cells as compared with thymic cells started to produce IgA later in fetal ontogeny, whereas the IgG response was not detectable in splenic cell culture media during the whole embryonal development and appeared only after birth. The earliest and the highest Ig stimulation was found after cultivation of lymphocytes with Nocardia delipidated cell mitogen. Interestingly, the moderate stimulatory effect of 65-kDa heat shock protein (Hsp-65) in polyclonal IgM response of fetal splenocytes was observed. We showed that thymic B lymphocytes represent probably the first maturing B cell population detectable in fetal life, which is able to differentiate after polyclonal stimulation into IgM as well as IgA and IgG producing cells.     

Antibodies to Klebsiella pneumoniae lipopolysaccharide in patients with ankylosing spondylitis

The role of microbial lipopolysaccharides (LPS) in the aetiopathogenesis of ankylosing spondylitis (AS) is a matter of continuing debate. In this study, class-specific IgG, IgA and IgM antibodies against Klebsiella pneumoniae, Escherichia coli, Salmonella typhimurium and Salmonella enteritidis LPS were measured by enzyme-linked immunosorbent assay (ELISA) in 100 AS patients, 50 rheumatoid arthritis (RA) patients and 50 healthy control subjects. The AS patients had significantly elevated levels of IgG and IgA antibodies against K. pneumoniae LPS (P < 0.001) and IgA antibodies against E. coli LPS (P < 0.05) compared to healthy controls. There were no significant elevations of antibody levels against S. typhimurium and S. enteritidis in the three study groups. In addition, there was a correlation between IgG and IgA anti-K. pneumoniae LPS antibody levels and the acute-phase reactant C-reactive protein (P < 0.001).     

Overexpression of c-myc induces apoptosis at the prophase of meiosis of rat primary spermatocytes

Serum samples from 36 cervical carcinoma patients, 33 patients with high-grade squamous intraepithelial lesions, and 31 cytologically normal women were tested by enzyme-linked immunosorbent assay (ELISA) using human papilloma virus type 6 (HPV 6) and HPV 16 virus-like particles as antigens. Forty serum specimens from 1-year-old children were used to assign cutoff points. When serum samples from the subjects infected with HPV 16 were tested in an HPV 16 ELISA detecting immunoglobulin A (IgA), IgG, and IgM binding, 61% showed IgA, 44% showed IgG, and 39% showed IgM reactivity. Of HPV 6- or 11- or HPV 18-infected subjects. fewer than 17% showed IgA or IgG responses and 33% showed IgM reactivity. In contrast, 13% showed IgA, 10% showed IgG, and 16% showed IgM reactivity in the HPV DNA-negative controls. The results suggest that the IgA and IgG responses are HPV 16 specific and the IgM response is cross-reactive to different HPV types. On the other hand, the serological responses to HPV 6 did not differ in the patient and control groups. The percentages of patients positive for both IgA and IgG antibodies were significantly higher in the groups with high-grade squamous intraepithelial lesions (12% [4 of 33]; P = 0.04) and cancer (17% [6 of 36]; P = 0.02) than in the healty women (0% [0 of 31]), and the percentages for either IgA or IgG were higher for the cancer group (47% [17 of 36]; P = 0.01) than in the normal group (19% [6 of 31]). Most sera positive for IgA and IgG in the patient groups showed higher titers than those in the normal group. All these results suggest that high IgA and IgG responses are good indicators for estimating HPV 16 infection.     

On the specificity of assays to detect circulating immunoglobulin A-fibronectin complexes: implications for the study of serologic phenomena in patients with immunoglobulin A nephropathy

Immunoglobulin A (IgA)-fibronectin complexes have been proposed as specific serologic markers of IgA nephropathy. They have been detected by the use of ELISA composed of an immobilized antifibronectin antibody (or albumin as a negative control) and an enzyme-conjugated anti-IgA antibody (antifibronectin capture assay). By the use of this type of assay, plasma samples from 32 normal controls, 38 IgA nephropathy patients, and 81 patients with other types of glomerulonephritis were analyzed. Extinction values in IgA nephropathy patients were higher (P = 0.06) than in patients with other glomerulonephritis types and significantly higher than in normals. Markedly lower values were obtained when the plates were coated with albumin. However, when the antifibronectin antibody was replaced by normal IgG or F(ab')2 fragments, almost identical extinctions were measured. The use of different antifibronectin antibodies, IgG, ELISA plates, or blocking regimens did not modify these results. Extinction values could not be suppressed by the addition of exogenous fibronectin. Similar extinctions were observed when plasma samples were replaced by physiologic concentrations of fibronectin-free IgA. Extinction values measured in the plasma samples correlated significantly with IgA concentrations in plasma as analyzed by nephelometry. A collagen binding assay, a second type of assay used to measure IgA-fibronectin complexes, also allowed the detection of fibronectin-free IgA, and again, extinctions measured in plasma could not be suppressed by exogenous fibronectin. In conclusion, both antifibronectin capture ELISA and collagen binding assays do not specifically detect only IgA-fibronectin complexes, but also total plasma IgA, which is frequently, but nonspecifically, elevated in IgA nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)     

The serological differentiation of acute and chronic schistosomiasis japonica using IgA antibody to egg antigen

Two groups of Schistosoma japonicum infected patients (acute and chronic) and non-infected individuals were studied using IgA antibody to egg antigen (SEA) and IgG and IgM antibodies to keyhole limpet haemocyanin (KLH). The means and standard deviation of the optical density in ELISA of acute, chronic and negative groups for IgA anti-SEA were 583 +/- 124.7, 98.2 +/- 78.8 and 82.2 +/- 39.3, respectively. There was a statistically significance between acute patients and chronic patients (P < 0.01). The means and standard deviation of IgG and IgM antibodies to KLH were 501.5 +/- 150.6, 113.0 +/- 79.1, 28.8 +/- 56.3 and 413.6 +/- 148.5, 70.2 +/- 14.8, 65.3 +/- 45.3, respectively. The detection results of IgA to SEA compared with the IgG and IgM to KLH did not demonstrate a significant difference (P < 0.01). The sensitivities of IgA to SEA and IgG and IgM antibodies to KLH for the detection of acute infection were 95.24%, 90.48% and 85.71%, respectively. Therefore, this study showed that the detection of IgA to SEA is also a useful new method for the serological differentiation of acute and chronic schistosomiasis japonica in humans.     

Culture and characterization of equine terminal arch endothelial cells and hoof keratinocytes

The occurrence of abnormally low serum immunoglobulin (Ig) levels is well-known in B chronic lymphocytic leukemia (CLL), but published data on IgG subclass levels are virtually absent. We measured serum IgG subclass levels in 52 B CLL outpatients, most in stage A and untreated, using an indirect immunoenzymatic assay with monoclonal antibodies. Mean levels of all Ig isotypes were lower than in normal controls in the whole group of patients, except for IgG2 in those studied at diagnosis. Levels of IgG1, IgG2, IgA, and IgM were lower in patients with a long disease duration than in those studied earlier. IgG subclass deficiencies occurred in 54% of cases and the most frequently affected isotype was IgG1. Every possible combination of IgG subclass and Ig class deficiencies from the selective deficiency of a single subclass to a combined deficiency of all isotypes was observed. This marked heterogeneity argues against the occurrence of isolated defects of one of the cytokines involved in Ig switching as a cause of hypoimmunoglobulinemia in CLL.     

Serological follow-up of patients with paracoccidioidomycosis treated with itraconazole using Dot-blot, ELISA and western-blot

Twenty-seven mycologically proven cases of paracoccidioidomycosis (PCM) were treated with itraconazole (100-200 mg/day in month 1 and 100 mg/day until month 6-8) and evaluated clinically and serologically, up to 3.5 years post-therapy, using Dot-blot and ELISA for measuring the titers of IgG, IgA and IgM anti-P.brasiliensis antibodies and Western-blot for determining IgG, IgA and IgM antibodies against the antigen components of the fungus. Before treatment, 81.5% (Dot-blot) and 84% (ELISA) of the patients presented elevated IgG anti-P.brasiliensis antibody titers which dropped slightly with treatment. On the other hand, the percentages of pre-treatment high-titered sera for IgA and IgM anti-P.brasiliensis were lower (51.9% and 51.8%: Dot-blot; 16.5 and 36%: ELISA, respectively) but the titers tended to become negative more frequently with treatment. Prior to treatment, the percentages of positivity for IgG, IgA and IgM anti-P.brasiliensis antibodies in Western-blot were 96%, 20.8% and 41.6%, respectively. Antigens with molecular weights varying from 16-78 kDa, from 21-76 kDa and from 27-78 kDa were reactive for IgG, IgA and IgM antibodies, respectively. The most frequently reactive antigenic components had molecular weights of 27, 33 and 43 kDa for IgG, and 70 for IgA and IgM antibodies. During the period of study, the patients responded well to treatment. The present data confirm the diversity and complexity of the humoral response in PCM, and the importance of utilizing different serological tests to detect IgG, IgA and IgM anti-P. brasiliensis antibodies.     

Regulation of thrombosis and hemostasis by antithrombin

An ELISA has been set up for quantifying mouse monoclonal antibodies in culture supernatant. The assay includes rabbit anti-mouse IgG antibodies chromatographycally purified. This preparation was used as coating and as conjugated antibodies in the ELISA. The assay can detect IgG1 with sensitivity of 0.2 ng/mL, IgG2a (0.85 ng/mL), IgG2b (0.13 ng/mL), and IgG3 (3.19 ng/mL) in culture supernatants. The effective working range was from subnanogram per mL quantities to 30 ng/mL by using a computer statistical program. Variation coefficient of ELISA was below 7%. Correlation estimates with a similar ELISA using commercial reagents were performed for each mouse antibody subclass. The assay was able to detect the four mouse monoclonal antibody subclasses in pure human serum as compared with the same ELISA using commercial antibodies. A 24-h pharmacokinetic profile of 1 patient treated with an IgG2a monoclonal antibody is presented.     

High-performance liquid chromatography-mass spectrometry-mass spectrometry analysis of morphine and morphine metabolites and its application to a pharmacokinetic study in male Sprague-Dawley rats

A high-performance liquid chromatography tandem mass spectrometry-mass spectrometry (LC-MS-MS) assay was developed for the analyses of morphine, morphine glucuronides and normorphine in plasma samples from rats. The analytes were extracted by using C2 solid-phase extraction cartridges. The extraction recoveries were 100% for morphine, 84% for morphine-3-glucuronide, 64% for morphine-6-glucuronide and 88% for normorphine. Both intra- and inter-assay variabilities were below 11%. Using a plasma sample size of 100 microliters, the limits of detection were 13 nmol l-1 (3.8 ng ml-1) for morphine, 12 nmol l-1 (5.5 ng ml-1) for morphine-3-glucuronide, 26 nmol l-1 (12 ng ml-1) for morphine-6-glucuronide and 18 nmol l-1 (5.0 ng ml-1) for normorphine, at a signal-to-noise ratio of 3. The present assay was applied to a pharmacokinetic study in rats after intraperitoneal administration of morphine.     

Energetics of vinca alkaloid interactions with tubulin isotypes: implications for drug efficacy and toxicity

Capture ELISAs, for canine IgG, IgM, IgA and albumin, were developed and used to analyse immunoglobulin (Ig) concentrations in both serum and secretions. Matched samples of serum, saliva and tears were taken from 31 dogs, assigned to two groups based on age, whilst bile samples were obtained from nine adult dogs at post-mortem. Serum and tear IgA concentrations were significantly lower in dogs < or = 12 months of age compared with dogs > 12 months of age (p = 0.006 and 0.045, respectively). There was no significant correlation between serum and secretory Ig levels, with the single exception of serum and tear IgM concentrations (rp = 0.553, p = 0.004). IgG and IgM concentrations were significantly correlated in matched tear and saliva samples (IgG: rp = 0.470, p = 0.023; IgM: rp = 0.651, p < 0.0001). Albumin concentrations were significantly correlated with IgG, but not IgM or IgA, in both saliva and tears (saliva, rp = 0.581, p = 0.004; tears, rp = 0.843, p < 0.0001) whilst IgA and IgM concentrations were significantly correlated with each other in both secretions (saliva, rp = 0.644, p = 0.001; tears, rp = 0.555, p = 0.009). Significantly, more Ig of all classes was secreted into saliva than tears as calculated by a secretory index. A large diurnal and day-to-day variation was observed in Ig concentrations in serial saliva and tear samples taken from a further four dogs. Serum Ig concentrations are therefore, poor indicators of mucosal secretion in this species and significant intra-individual variation exists in secretory Ig levels. Both findings should be taken into account in future studies of canine mucosal immunoglobulins.     

The pathogenesis of alcoholic liver disease

The immunoglobulin (Ig) isotype (IgG, IgA, IgM) production of peripheral blood mononuclear cells from 28 patients having multiple myeloma (MM) was analyzed. The total Ig secreting capacity of the cells, as measured by ELISA from the cell culture medium, was not found to be significantly reduced in MM (1,118 +/- 1,394 micrograms/l) as compared to the values of 9 controls (898 +/- 520 micrograms/l), but a significant isotype switching towards the tumor paraprotein type was observed in the patients with active MM (p < 0.001). The percentage of IgG in the active IgG-MM was 88 +/- 11% and that of IgA in the active IgA-MM 83 +/- 13%, the control values being 44 +/- 11% for IgG and 44 +/- 13% for IgA. The proportions of isotypes resembled those of the controls in the inactive phase of the disease. Despite this dominating paraprotein class isotype production, no evidence of Ig gene clonal rearrangements was found in cells studied by either Southern blotting or the more sensitive polymerase chain reaction method, which suggests that polyclonal rather than monoclonal PB B cells are responsible for the Ig production observed.     

Brownian dynamics study of ion transport in the vestibule of membrane channels

The Immunoglobulin (Ig) binding capacity of Toxoplasma gondii tachyzoites was investigated using fluorescence flow-cytometry analysis. Polyclonal mouse, human and rat immunoglobulins without specific anti-Toxoplasma activity bound to parasites in a concentration-dependent manner, saturating them at circulating serum concentrations. The immunoglobulin class and subclass specificity of binding was investigated using irrelevant monoclonal antibodies. IgM, IgA and IgG reacted with the parasite membrane. The attachment of mouse IgM to the parasite surface was hampered by mouse IgG1, IgG2a, IgG2b and IgG3. The binding of mouse IgG was proportionally reduced with increasing concentrations of mouse monoclonal IgM. The binding of murine immunoglobulin was diminished when in presence of human IgG. Purified Fc- but not Fab portions of immunoglobulins, fixed to parasites. Using labelled calibrated beads, the Ig binding capacity of parasites was estimated to be 6900 +/- 500 sites per tachyzoite. The Kd of the T. gondii Fc Receptor (FcR) activity was determined at 1.4 +/- 0.1 microM (mean +/- SEM). Such FcR activity was reduced by phospholipase C, trypsin and pronase treatment of the parasites. These data show a low affinity FcR activity on T. gondii tachyzoites which recognizes Ig of different species and isotypes and is likely supported by a glycosyl-phosphatidylinositol (GPI)-anchored surface protein of the parasite.     

Detection of serum antibodies against Chlamydia pneumoniae by ELISA

Chlamydia pneumoniae causes pneumonia and other respiratory infections in children, adolescents and adults. We tried to evaluate the diagnostic value of detection of serum antibodies by ELISA for C. pneumoniae infections in Japanese children. Serum IgG, IgA and IgM antibodies to C. pneumoniae were determined by the microimmunofluorescence (MIF) test. Serum IgG and IgA antibodies were also determined by ELISA test kits. Results obtained by ELISA were compared with those obtained by MIF test. IgG antibody to C. pneumoniae was detected in 135 (39.5%) by ELISA and in 125 (36.5%) by MIF out of 342 sera from Japanese infants and children without respiratory infections (aged from 2 months old to 15 years old). IgA antibody to C. pneumoniae was detected in 129 (37.7%) by ELISA and in 117 (34.2%) by MIF out of 342 sera tested. Of 342 specimens 113 were IgG-positive by ELISA and MIF (sensitivity: 90.4%, specificity: 89.9%, r = 0.853). Of 342 sera 28 had IgG antibody titers of 1:256 and none had titers 1:512 or higher by MIF. Of 28 infants and children a total of nine were less than 4 years of age. On the other hand, of 342 specimens 99 were IgA-positive by ELISA and MIF (sensitivity: 84.6%, specificity: 86.7%, r = 0.769). Of 342 sera 16 had IgA antibody titers of 1:256 or higher by MIF. Of 16 infants and children, ten were less than 4 years of age. ELISA had excellent sensitivity and specificity relative to MIF test for detection of IgC and IgA antibodies to C. pneumoniae. It was suggested that C. pneumoniae infection in Japanese infants and children under 4 years of age was not infrequent.     

Human and nonhuman primate lymphocytes engrafted into SCID mice reside in unique mesenteric lymphoid structures

The present study compares the location and phenotype of B lineage lymphocytes in tissues from SCID mice engrafted with PBMC of human, chimpanzee, and pig-tailed macaque origin. In mice repopulated with both human and nonhuman primate lymphocytes, plasma cells were found in the peritoneal cavity in vascularized structures located in the mesentery near the pancreas, intestines, and spleen. The predominant isotype of the plasma cells was IgG; IgM and IgA cells were also present. Kappa and lambda light chains were expressed by 62% and 38% of the Ig-containing cells, respectively. J chain expression occurred in most cells irrespective of the Ig isotype. In the SCID mice engrafted with human lymphocytes, a few IgM-containing cells were found in the spleen; plasma cells were not found in other tissues, including the intestine. The aggregation of plasma cells did not appear to be a result of infection with EBV. T cells were rarely found in the lymphoid aggregates but were recovered from the spleen and peritoneal lavage. Human Ig levels in the serum of engrafted mice reflected the isotype distribution of the cells with IgG > IgM > or = IgA.     

Studies on translocation of immunoglobulins across intestinal epithelium. II. Immunoelectron-microscopic localization of immunoglobulins and secretory component in human intestinal mucosa

To define mechanisms involved in the transport of immunoglobulins into intestinal fluids, we localized IgM, IgA, IgG, and secretory component (SC) in human intestinal mucosa by the peroxidase-labeled antibody technique. At the light microscopic level, immunocytes containing IgA, IgM, or IgG were found in the lamina propria. IgA, IgM, and SC were prominent in the epithelium of gland crypts; IgG was limited to a few cells at tips of villi. At the electron-microscopic level, SC was localized to perinuclear spaces, endoplasmic reticulum, saccules associated with Golgi complexes, cytoplasmic vesicles, and lateral and basal plasma membranes of columnar epithelial cells. IgA and IgM, but not IgG, also were localized to plasma membranes and cytoplasmic vesicles of these cells. Neither the immunoglobulins nor SC was found within other types of epithelial cells (Paneth, goblet, endocrine). The findings provide evidence that (1) the site of SC synthesis in intestinal epithelium is secretory columnar cells, principally those in gland crypts; (2) the polymeric immunoglobulins IgM and IgA are translocated through such SC-containing cells by a process that involves formation of cytoplasmic vesicles; (3) IgM and IgA could combine with SC during transcellular transport (likely sites are lateral or basal plasma membranes or supranuclear cytoplasm); (4) the monomeric immunoglobulin IgG does not share the transepithelial cell route involved in IgM and IgA transport.