Some in vivo effects of pi mesons in mice

The effect of 70 MeV pi mesons was studied to determine the effectivness of such beams aginst normal tissues in vivo. The end points included thymic weight loss, oocyte and bone marrow CFU-S survival and the induction of macroscopid lens opacities. The results indicate that pi mesons are not signifacantly more effective for these end-points than more conventional radiation sources such as 60Co gama rays, 220 kVp X rays, and 14 MeV X rays and electrons. Nor was there any detectable difference in RBE between the peak and plateau regions of the pi meson beam. The significance of these findings is discussed in relation of the the published pi meson RBE values of between 1 therefore 4 and 5 therefore 0.     

Dysregulation of the humoral immune response in old mice

The increase in autoantibodies with age of both experimental animals and humans has been thought to reflect a shift in the antibody repertoire from foreign to self antigens. In mice, before immunization, the age-associated increase in antibodies reactive with a prototypic autoantigen, bromelain-treated autologous erythrocytes (BrMRBC), reflected a 3-fold increase in serum IgM and the number of IgM-secreting spleen cells in old compared with young mice. However, the percentage of the IgM-secreting spleen cell repertoire reactive with BrMRBC in old mice was actually approximately 50% that in young mice. In contrast, after immunization with sheep erythrocytes (SRBC), old mice showed a 5-fold increase in the percentage of IgM-secreting cells reactive with BrMRBC while young mice showed no significant increase. The converse is true for the percentage of IgM-secreting spleen cells in old mice specific for SBRC, which is 10% the number generated by young mice. The increased autoantibody response of old mice is not, however, linked to their poor response to the nominal antigen. Thus, immunization with phosphorylcholine (PC) conjugated keyhole limpet hemocyanin, an antigen that induces a comparable anti-PC response in old and young mice, also induced more autoantibody forming cells in old than young mice. The increased autoantibody response of old mice after immunization can be accounted for by both an increased number of Ig-secreting spleen cells as well as an increased percentage of the expressed repertoire of IgM-secreting spleen cells that react with autoantigens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chromosome aberrations in human fibroblasts induced by monoenergetic neutrons. I. Relative biological effectiveness

The relative biological effectiveness (RBE) of neutrons for many biological end points varies with neutron energy. To test the hypothesis that the RBE of neutrons varies with respect to their energy for chromosome aberrations in a cell system that does not face interphase death, we studied the yield of chromosome aberrations induced by monoenergetic neutrons in normal human fibroblasts at the first mitosis postirradiation. Monoenergetic neutrons at 0.22, 0.34, 0.43, 1, 5.9 and 13.6 MeV were generated at the Accelerator Facility of the Center for Radiological Research, Columbia University, and were used to irradiate plateau-phase fibroblasts at low absorbed doses from 0.3 to 1.2 Gy at a low dose rate. The reference low-LET, low-dose-rate radiation was 137Cs-gamma rays (0.66 MeV). A linear dose response (Y = alphaD) for chromosome aberrations was obtained for all monoenergetic neutrons and for the gamma rays. The yield of chromosome aberrations per unit dose was high at low neutron energies (0.22, 0.34 and 0.43 MeV) with a gradual decline with the increase in neutron energy. Maximum RBE (RBEm) values varied for the different types of chromosome aberrations. The highest RBE (24.3) for 0.22 and 0.43 MeV neutrons was observed for intrachromosomal deletions, a category of chromosomal change common in solid tumors. Even for the 13.6 MeV neutrons the RBEm (11.1) exceeded 10. These results show that the RBE of neutrons varies with neutron energy and that RBEs are dissimilar between different types of asymmetric chromosome aberrations and suggest that the radiation weighting factors applicable to low-energy neutrons need firmer delineation. This latter may best be attained with neutrons of well-defined energies. This would enable integrations of appropriate quality factors with measured radiation fields, such as those in high-altitude Earth atmosphere. The introduction of commercial flights at high altitude could result in many more individuals being exposed to neutrons than occurs in terrestrial workers, emphasizing the necessity for better-defined estimates of risk.     

The normalization of the immune response in old stressed mice by apomorphine

A case of Rochalimaea henselae infection in an AIDS patient is reported. The R. henselae infection was revealed by febrile pancytopenia associated with liver and spleen enlargement. The diagnosis was made on the finding at histology of hepatic peliosis lesions. Within these lesions Warthin Starry staining displayed bacilli that were identified as R. henselae. This case shows that all HIV-infected patients with these symptoms might be infected with this organism.     

Rosette-forming cells during immune response to Toxoplasma gondii in mice

The rosette-forming cell (RFC) response of mice immunized with varying doses of Toxoplasma gondii was studied by immunocytoadherence (ICA). The specificity of ICA in the present system was tested by passive sensitization with hyperimmune serum in vivo and in vitro. A slight increase in RFC was observed with the latter. Prior treatment of spleen cells from immunized animals with rabbit anti-mouse immunoglobulin resulted in total inhibition of ICA. During the primary and the secondary response after 10 days, the number of RFC rose rapidly to reach the peak on the 3rd day. With secondary immunization 30 days later, the peak shifted to the 2nd day. Mice infected with a lower dose of Toxoplasma had a greater number of RFC during the secondary response after 10 days than with a larger dose.     

An in vitro model for infection with Leishmania major that mimics the immune response in mice

By using a primary in vitro response specific for Leishmania major, normal T cells from resistant CBA/CaH-T6J and susceptible BALB/c mice commit to a Th1 and a Th2 response, respectively. Since commitment occurred, we measured the production of gamma interferon (IFN-gamma), interleukin-1 (IL-1), IL-2, IL-4, IL-5, IL-10, and IL-12, prostaglandin E2 (PGE2), transforming growth factor beta (TGF-beta), and nitric oxide in the first 7 days of the response to identify factors that are critical for Th1 and Th2 development. While cells from resistant CBA mice produced more IFN-gamma, IL-10, and nitric oxide, cells from susceptible BALB/c mice produced more IL-1alpha, IL-5, PGE2, and TGF-beta. Although substantial amounts of IL-12 were detected, IL-12 did not associate with either Th1 or Th2 development. We did not anticipate that cells from resistant CBA mice would make more IL-10 in vitro. However, this also occurred in vivo since CBA mice produced substantial amounts of IL-10 following infection with L. major. Moreover, adding anti-IL-10 to primary in vitro responses enhanced production of IFN-gamma and nitric oxide by cells from CBA and BALB/c mice. Therefore, IL-10 cannot be regarded as a cytokine that associates with susceptibility to infection with L. major. Finally, the data presented here suggest that a collection of factors that can be produced by accessory cells influence Th commitment (e.g., IL-1, PGE2, and TGF-beta favor Th2 development).     

Severe attenuation of the B cell immune response in Msh2-deficient mice

Recently, results obtained from mice with targeted inactivations of postreplication DNA mismatch repair (MMR) genes have been interpreted to demonstrate a direct role for MMR in antibody variable (V) gene hypermutation. Here we show that mice that do not express the MMR factor Msh2 have wide-ranging defects in antigen-driven B cell responses. These include lack of progression of the germinal center (GC) reaction associated with increased intra-GC apoptosis, severely diminished antigen-specific immunoglobulin G responses, and near absence of anamnestic responses. Mice heterozygous for the Msh2 deficiency display an "intermediate" phenotype in these regards, suggesting that normal levels of Msh2 expression are critical for the B cell response. Interpretation of the impact of an MMR deficiency on the mechanism of V gene somatic hypermutation could be easily confounded by these perturbations.     

Immunoglobulin deficient mice generated by gene targeting as models for studying the immune response

B cell deficient animals obtained by various strategies of gene targeting were used to study the B cell development and examine the role of different immune compartments in the immune response to microbes. Study of muMT, JHD, lambda 5T and JHT models of B cell deficiency, was essential in order to understand the role of pre-B cell receptor in B cell development, allelic exclusion and variable gene rearrangement regulation. In the immune response to influenza virus, a protective role of T cells in a total absence of B cell compartment, was revealed by studying the JHD -/- model. Further, it was established that a T cell compartment is sufficient to mediate the recovery from influenza infection. Examination of immune response in muMT and JHD models of definitive B cell deficiency to various blood stage Plasmodia species, showed that whereas B cells are not required for recovery from infection with P. chabaudi adami, P. vinckei petteri and P. chabaudi chabaudi (CB), B cell compartment is important in the later stages of infection with P. chabaudi chabaudi (AS). Studies carried out in muMT model suggested a possible role for T gamma delta subpopulation in the immune response to blood stage malaria parasite. B cell deficiency models are valuable for understanding the normal and pathological immune response. Studies carried out in muMT model indicated that T cell responses are not significantly affected in the absence of B cells. These data can neither rule out a role for B cells in T cell priming, nor in triggering an effective T cell help for humoral response. Study of double homozygous mice deficient for B cells and FAS or IL-2 gene, pinpointed the role of B cells in pathogenesis of lupus-like nephritis and vasculitis from lpr mouse and in hemolytic anemia from IL-2 -/- mouse model, respectively.     

Inhalatory anesthetic (halothane) associated changes in the immune response in mice

The extent of surgery, the patient's age, health status and other factors may contribute to alteration of the immune system during anesthesia and surgery. In addition, inhalatory anesthetics may cause acute and chronic toxicity because of the production of intermediate and end metabolic compounds. The present work was undertaken to evaluate, both in vivo and in vitro, if repeated doses of halothane were able to affect the immune response in a murine model developed at our laboratory. Weekly doses of halothane were administered to mice subjected to no surgery and three days after the last anesthetic-exposure, several immunologic parameters were assessed. Results on the in vivo response to sheep red blood cells showed that halothane treatment increased the amount of specific antibody secreting B-cells, without affecting the delayed type hypersensitivity reaction to the same antigen. In vitro studies on spleen cell composition showed that halothane re-exposure diminished the number of CD4+, CD8+ and B-cells. Such changes were not translated into alterations on the mitogen-driven lymphoproliferation, as well as macrophage phagocytic and lytic functions. Our results indicate that halothane re-exposure is able to modulate the immune response affecting both the number of antibody secreting cells involved in a specific in vivo response, and the splenic lymphoid cell composition. Since such halothane-induced immune alterations might bias the results of a wide range of physiological research, even those involving other systems, a careful selection of the anesthetic agent and methods by which the compound is administered is advisable.     

Eosinophil-enriched inflammatory response to schistosomula in the skin of mice immune to Schistosoma mansoni

Exposure of the mouse skin to Schistosoma mansoni cercariae gives rise to acute, exudative inflammation in both normal and immune mice, but the immune response is anamnestically accelerated and is oesinophil-enriched, thereby enhancing opportunities for tegumental contact of schistosomula with host leukocytes, particularly with eosinophils. Many of the inflammatory changes occurring within the first 48 hours after exposure are due to cercarial products, e.g., "penetration tracts," but some remain demonstrable when schistosomula metamorphosed in vitro are injected intradermally and are therefore directed against the schistosomula themselves, such as the leukocyte "streaming patterns" seen in their pathways. In contrast to earlier observations in primates, cellular responses to schistosomula in the mouse lung 4 days after penetration are minimal in either normal or immune mice. Thus, immune cellular responses to schistosomula in mice are limited to an early time period after cercarial penetration and are morphologically suggestive of an antibody-mediated response rather than of delayed hypersensitivity. Our observations complement earlier evidence suggesting that antibody-mediated host leukocyte contact with schistosomula initiates the killing of challenge parasites in immune mice, with the eosinophil probably playing a crucial role.     

Regulation of the immune system by synthetic polynucleotides. VI. Amplification of the immune response in young and aging mice

Model systems for study of the action of adjuvants in immunodeficient states were developed in 10- to 14-day-old BALB/aj mice and aging BALB/aj mice (12 to 16 months). With sheep red blood cells as antigen polyadenylicpolyuridylic acid complexes (poly A:U) were found to be stimulatory in both the neonatal and aging mice. The effect of poly A:U was similar to that seen when 5 X 10(6) thymocytes from immunologically mature mice were given with antigen. Cell-free supernatant fluids induced by incubation of poly A:U with thymocytes likewise were capable of restoring the number of antibody-forming cells to normalcy in aging mice.     

Zinc and metallothioneins on cellular immune effectiveness during liver regeneration in young and old mice

Partial hepatectomy in young mice (pHx) induces thymic atrophy, disregulation of thymocytes subsets and a strong accumulation of zinc in thymic tissue after 1-2 days of liver regeneration. Zinc is relevant for good immune functioning. Restoration of zinc into both the thymus and thymocytes subsets in the late period of liver regeneration is observed in young pHx mice. These findings have suggested a link between the thymus and the liver influencing T-cell functions and involving zinc. This kind of link could be relevant in aging because thymic involution, negative crude zinc balance and crippled immune functions are constant events. The preminence of a liver extrathymic T-cell pathway after pHx or during aging has been suggested. Thus the study of pHx in young and old mice may offer a good model to better understand the role played both by thymic involution and by liver extrathymic T-cell pathway and the role of zinc in these physiological processes during aging. Young pHx mice after 1-2 days of liver regeneration show: reduced thymic endocrine activity, increment of double negative (DN) thymocytes subsets, impairment of peripheral immune efficiency (PHA, NK activity and IL-2) and negative crude zinc balance, which are all restored in the late period of liver regeneration. By contrast the thymic and peripheral immune defects and the negative crude zinc balance, already present in old sham mice, are not modified during liver regeneration in old pHx mice. Circulating leukocytes and lymphocytes are not significantly modified both in young and old pHx mice as compared to respective sham controls. Zinc may also be crucial for extrathymic T-cells pathway, being preminent in aging, rather than in young age, due to its metallothioneins (MT) binding capacity. MT are significantly increased in young pHx and in aging inducing a low zinc-free quota for thymic and peripheral immune efficiency in young pHx mice, and for extrathymic T-cell pathway, in old age. Thus low zinc bioavailability, due to MT, may play a pivotal role, not only for thymocytes but also for liver extrathymic T-cell pathway.     

The immune response to Plasmodium chabaudi malaria in interleukin-4-deficient mice

Interleukin(IL)-4 promotes the development of T helper (TH)2 cells, induces immunoglobulin class switching to IgG1 and is thought to be essential for switching to IgE. During a primary infection with the erythrocytic stages of Plasmodium chabaudi chabaudi, TH1 and TH2 cells specific for the parasite appear sequentially as infection progresses. To dissect the possible role of TH2 responses at the later stages of infection, mice with a targetted disruption of the IL-4 gene were infected with P. chabaudi. IL-4-deficient mice were able to control and clear a primary infection, although recrudescent parasitemias were significantly higher in these mice compared with wild-type littermates; demonstrating that IL-4 per se is not required for parasite elimination. To evaluate the actual impairment of TH2 functions in the absence of IL-4 in vivo during an infection with P. chabaudi; the cellular and humoral responses to the parasite generated in vitro and in vivo were compared in the two types of mice. Our data indicate that in vitro TH1 responses and ex vivo IL-12 mRNA levels were sustained in the IL-4-deficient mice compared with wild-type littermates. Correspondingly, TH2-associated cytokine mRNA such as IL-5 and IL-6, but not IL-10, were reduced early in infection in the deficient animals. However, these cytokines were expressed at comparable levels at the later stages of infection in both types of mice. Reflecting these differences in TH function, IgG1 responses were decreased in vitro and delayed in vivo, whereas IgG2a and IgG2b responses appeared earlier in vivo in the deficient mice. Strikingly, IgE secretion was not blocked in vivo in the deficient mice; the onset of the synthesis of IgE mRNA was delayed during infection and the amount of circulating IgE was five times lower than in the wild-type littermates after 5 weeks of infection. All these impairments of TH2-related activities were insufficient to affect parasite clearance in the deficient mice, probably due to the fact that such activities were only delayed and could take place normally at the later stages of infection.