Relative size and evolution of the germline repertoire of T-cell receptor beta-chain gene segments in nonhuman primates

Comparison of the expressed porcine Vbeta and Jbeta repertoire of thymocytes and peripheral T cells

Transcripts of more than 300 unique T-cell receptor-beta (TCR-beta) V-D-J rearrangements recovered from porcine thymocytes and peripheral T cells were compared. We identified 19 groups (families) of porcine Vbeta genes in seven supergroups and provisionally named 17 groups based on their sequence similarity with recognized human Vbeta gene families. TRBV4S, 5S, 7S and 12S accounted for >80% of all Vbeta usage, and usage of these groups by thymocytes and peripheral T cells was highly correlated. No TRBV group was uniquely expressed in significant numbers in thymocytes, although small numbers of TRBV groups 2S, 9S and 15S were only recovered from T cells. Usage of Jbeta segments from the 5' D-J-C duplicon in thymocytes and peripheral T cells directly correlated with their 5' position in the locus, and Jbeta1.1, 1.2 and 1.3 accounted for >or= 35% of all Jbeta usage in both cell types. This contrasts with the usage of Jbeta2 segments in that Jbeta2.4, 2.5 and 2.7 accounted for approximately 30% of Jbeta usage by T cells and thymocytes. Jbeta2.7 was threefold more frequent among T cells than thymocytes. The Vbeta/Jbeta combination was not random. Jbeta1.1 and 1.2 were used in 29% of rearrangements with high frequency among the major Vbeta groups. Combinations of TRBV4 and V12 with Jbeta2.7 were only found in T cells and accounted for half of all Jbeta2.7 usage. These studies show that unlike porcine heavy chain V(H) genes, the occurrence and relative usage of porcine TCR-Vbeta groups resembles that of humans. Thus, highly related gene systems can individually diverge within a species.

Characterization of expanded T cell clones in healthy macaques: ontogeny, distribution and stability

Peripheral expanded T cell clones have been discussed mainly in relation to certain diseases or immune function in humans and mice. There is little information on their ontogeny, stability and distribution among T cell subsets as well as major lymphoid organs. We applied reverse transcription-polymerase chain reaction (RT-PCR) with family specific primers for monkey T cell receptor beta chain V regions and single-strand conformation polymorphism (SSCP) analysis to analyze the expanded T cell clones in cynomolgus monkeys (Macaca fascicularis). A number of expanded T cell clones were detected in the peripheral blood of young and adult monkeys, but few expanded T cell clones were detected in the blood of a fetus and a 2-day-old neonate. The clones in adults were maintained over 3 months. These expanded T cell clones were distributed only in peripheral blood and spleen, but few were found in lymph nodes (axillary, inguinal and intestinal). The number of expanded T cell clones was much greater in CD8 single-positive (CD8sp) T cells than in CD4sp T cells, showing that most of these clones originated in the CD8sp T cell population. Almost all the expanded CD8sp T cell clones belonged to the CD28(-), CD29(hi) and Fas(+) subset. The usage of V beta genes was not skewed in the 24 V beta. Furthermore, higher mRNA signals for effector molecules perforin and IFN-gamma were detected in CD8sp T cell subsets with phenotypes of CD28(-), CD29(hi) and Fas(+), suggesting that the expanded T cells might have developed in relation to T cell activation in the periphery of cynomolgus monkeys.

Structure and content of the major histocompatibility complex (MHC) class I regions of the great anthropoid apes

The origins of the functional class I genes predated human speciation, a phenomenon known as trans-speciation. The retention of class Ia orthologues within the great apes, however, has not been paralleled by studies designed to examine the pseudogene content, organization, and structure of their class I regions. Therefore, we have begun the systematic characterization of the Old World primate MHCs. The numbers and sizes of fragments harboring class I sequences were similar among the chimpanzee, gorilla, and human genomes tested. Both of the gorillas included in our study possessed genomic fragments carrying orthologues of the recently evolved HLA-H pseudogene identical to those found in the human. The overall megabase restriction fragment patterns of humans and chimpanzees appeared slightly more similar to each other, although the HLA-A subregional megabase variants may have been generated following the emergence of Homo sapiens. Based on the results of this initial study, it is difficult to generate a firm species tree and to determine human's closest evolutionary neighbor. Nevertheless, an analysis of MHC subregional similarities and differences in the hominoid apes may ultimately aid in localizing and identifying MHC haplotype-associated disease genes such as idiopathic hemochromatosis.