T-cell receptor variable beta genes show differential expression in CD4 and CD8 T cells.

Studies in transgenic and inbred strains of mice have shown that the critical molecular interactions controlling positive selection involve major histocompatibility complex (MHC), T-cell receptor (TCR), and CD4 or CD8 coreceptor molecules. Correlations have been established between MHC gene products and the percentage of CD4 or CD8 T cells that express specific variable (V) beta-gene products as part of the alpha beta heterodimer. These studies have important implications regarding potential mechanisms of HLA-linked autoimmune diseases in humans. If similar interactions are required for positive selection in humans, one would predict that the TCR repertoire expressed by mature, peripheral blood CD4 and CD8 T cells would vary. To test this hypothesis the expression of specific TCR V beta-region genes by CD4 and CD8 T cells from healthy individuals was compared using both triple-color flow cytometry and polymerase chain reaction based experimental approaches. The results show that the TCR repertoire does vary as a function of CD4 and CD8 T-cell subsets. Among unrelated individuals certain V beta genes were consistently overrepresented in the CD4 population (V beta-5.1, -6.7a, and -18); some were skewed to the CD8 population (V beta-14) while others showed variable patterns (V beta-12 and -17). Deletion of entire V beta gene families was not observed suggesting that this is a rare event in humans. Attempts to correlate the expressed TCR repertoire in humans with HLA alleles will require consideration of these differences in expression as a function of subset.

Patterns of T-cell receptor variable beta gene expression by synovial fluid and peripheral blood T-cells in rheumatoid arthritis.

Conflicting data have been reported regarding the presence or absence of a predominant variable (V) region T-cell receptor (TCR) gene in the peripheral blood or synovial fluid of patients with rheumatoid arthritis (RA). In this study we have used the polymerase chain reaction (PCR) to compare the level of TCR V beta gene expression by peripheral blood mononuclear cells (PBMC) and by synovial fluid cells obtained from HLA DRB1 *0401 and *0404 RA patients. PCR was performed using cDNA synthesized from freshly obtained cells (not stimulated in vitro). The pattern of expression observed for most of the V beta genes studied showed either preferential expression by PBMC or similar levels of expression between PBMC and synovial fluid T-cells. However, among individual patients (N = 5), several V beta genes were identified that were expressed to a significantly greater degree by synovial fluid cells. V beta 14 expression was detected in PBMC of all patients and the level of transcripts encoding V beta 14 increased following stimulation with immobilized anti-CD3 and IL-2. In vitro manipulation of populations of T-cells was found to alter the level of expressed V beta gene products. A V beta gene common to all patients that was consistently deleted from PBMC or expressed to a greater degree by resident, unsorted synovial fluid cells compared to PBMC was not identified.

High-pressure liquid chromatographic analysis of hemolymph plasma catecholamines in immune-reactive Aedes aegypti.

Tyrosine and catecholamines have been implicated as substrates for the encapsulation reactions involved in the immune response of mosquitoes to microfilariae (mff). Identification and quantitation of tyrosine and catecholamines present in Aedes aegypti hemolymph plasma were accomplished by ion-pair high-pressure liquid chromatography with electrochemical detection at either +650 or +850 mV vs Ag/AgCl. Tyrosine, dopamine, and N-beta-alanyldopamine were detected in the hemolymph plasma of naive A. aegypti. Although no differences in these compounds were observed in hemolymph plasma from A. aegypti inoculated with Dirofilaria immitis mff, the chromatogram showed a single major peak (PI) (65 microM, expressed as dopamine equivalents) that was not present in naive hemolymph plasma. Saline-inoculated controls contained only 5% of the PI in immune reactive hemolymph plasma. A high concentration of PI (127 +/- 39 microM) was also detected after treatment of hemolymph plasma with mild alkaline conditions (pH 9.0), indicating that it is normally present as an electrochemically inert form in naive mosquitoes. High concentrations of PI were also detected in the naive hemolymph plasma from three other mosquito species, but no PI was found in A. trivittatus under any conditions. PI did not cochromatograph with any of the catecholamines commonly thought to be involved in immune responses of dipterans against metazoan parasites, suggesting that it may be a unique substrate for these reactions. The biological relevance of PI was evidenced by its appearance in the hemolymph plasma of two strains of D. immitis-inoculated A. aegypti.