Specific recognition of HLA-E, but not classical, HLA class I molecules by soluble CD94/NKG2A and NK cells

The CD94/NKG2 receptors expressed by subpopulations of NK cells and T cells have been implicated as receptors for a broad range of both classical and nonclassical HLA class I molecules. To examine the ligand specificity of CD94/NKG2 proteins, a soluble heterodimeric form of the receptor was produced and used in direct binding studies with cells expressing defined HLA class I/peptide complexes. We confirm that CD94/NKG2A specifically interacts with HLA-E and demonstrate that this interaction is dependent on the association of HLA-E with peptide. Moreover, no interaction between CD94/NKG2A and classical HLA class I molecules was observed, as assayed by direct binding of the soluble receptor or by functional assays using CD94/NKG2A+ NK cells. The role of the peptide associated with HLA-E in the interaction between HLA-E and CD94/NKG2A was also assessed. All class I leader sequence peptides tested bound to HLA-E and were recognized by CD94/NKG2A. However, amino acid variations in class I leader sequences affected the stability of HLA-E. Additionally, not all HLA-E/peptide complexes examined were recognized by CD94/NKG2A. Thus CD94/NKG2A recognition of HLA-E is controlled by peptide at two levels; first, peptide must stabilize HLA-E and promote cell surface expression, and second, the HLA-E/peptide complex must form the ligand for CD94/NKG2A.     

Results of transition zone biopsy in black and white men with suspected prostate cancer

OBJECTIVES: To determine whether biopsy-detectable transition zone tumors are more common in black than in white men with suspected Stage T1c and T2 prostate cancer. METHODS: We performed a prospective study of transition zone prostate biopsy (TZ biopsy) in 1 78 black and 261 white men who had not undergone previous prostate biopsy and in 61 black and 65 white men who had undergone one benign sextant peripheral zone prostate biopsy (PZ biopsy). RESULTS: The mean age of the 239 black and 326 white study patients was 68.6+/-7.4 and 67.2+/-7.2 years, respectively (P = 0.02), the mean prostate-specific antigen (PSA) was 8.4+/-7.4 and 6.4+/-5.4 ng/mL, respectively (P = 0.003), and the mean PSA density was 0.20+/-0.23 and 0.16+/-0.16 ng/mL/mL, respectively (P = 0.006). Overall, cancer was diagnosed by TZ biopsy only in 7 black men (3%) and in no white men (0%) (P = 0.003). However, cancer detection with a TZ biopsy only was not significantly different in the black and white men when controlled for age, PSA, or PSA density (P>0.90). A TZ biopsy only detected cancer in 1% of patients who had not undergone prior PZ biopsy and in 2% of patients who had undergone prior PZ biopsy. Of the seven cancers detected with TZ biopsy, six (86%) had a Gleason score of 2 to 6. CONCLUSIONS: Prostate cancer detection with a TZ biopsy only is not common and when controlled for confounding variables is the same in black and white men. The preferential use of TZ biopsies in black men is not warranted, and the low diagnostic yield argues against routine use of the biopsy technique in men of either race.     

Comparison of teaching the basic electrocardiographic concept of frontal plane QRS axis using the classical versus the orderly electrocardiogram limb lead displays

This study compares the effectiveness of teaching the calculation of frontal plane QRS axis with the use of the classical versus the orderly electrocardiographic limb lead display. Eighty-three students from two environments were randomized into two groups and were taught to determine frontal plane axis with one of the methods. The accuracy and time to determine the axis were tested on 10 electrocardiograms. In the United States the group using the classical display achieved 4.2 (+/-2.7) correct answers, whereas those using the orderly method achieved 6.8 (+/-3.0) (p = 0.0006). The classical group used 9.2 (+/-2.8) minutes to complete the test, whereas the orderly group needed 7.2 (+/-2.0) minutes (p = 0.015). The results achieved in Sweden were similar. The use of the orderly electrocardiographic limb lead display results in greater diagnostic accuracy in less time than the classical display when determining the frontal plane QRS axis.     

Metabolic consequences of phosphotransferase (PTS) mutation in a phenylalanine-producing recombinant Escherichia coli

E. coli strain PPA305, which has a wild-type PTS system, and PPA316, which utilizes a proton-galactose symport system for glucose uptake, were used as host strains to harbor a phenylalanine overproduction plasmid pSY130-14 and to study the effects of using different glucose uptake systems on phenylalanine production. The non-PTS strain (PPA316/pSY130-14) produced much less phenylalanine, ranging from 0 to 67% of that produced by the PTS strain (PPA305/pSY130-14) depending on cultivation conditions used. The non-PTS strain PPA316/pSY130-14 had an intracellular PEP concentration only one-sixth that of the PTS strain, PPA305/pSY130-14. Additionally, PPA316/pSY130-14 had a substantially lower energy state in terms of the size of the pool of high-energy phosphate compounds and the magnitude of the pH difference across the cytoplasmic membrane. The non-PTS strain consumed oxygen at a higher rate, attained lower biomass concentration, and produced no acetate and phenylalanine during fermentation, suggesting more carbon was oxidized to CO2, most likely through the TCA cycle. Analysis of intracellular fluxes through the central carbon pathways was performed for each strain utilizing exponential phase data on extracellular components and assuming quasi-steady state for intermediate metabolites. The non-PTS strain had a higher flux through pyruvate kinase (PYK) and TCA cycle which, in agreement with the observed higher oxygen uptake rate, suggests that more carbon was oxidized to CO2 through the TCA cycle. Further analysis using rate expression data for PYK and NMR data for the intracellular metabolites identified the regulatory properties of PYK as the probable cause for lower intracellular PEP levels in PPA316/pSY130-14.