Human CD4-8- -derived clones. Phenotypic and functional characteristics and variation between donors in patterns of T-cell receptor gamma gene rearrangements

T cell receptor junctional regions of V gamma 9+/V delta 2+ T cell clones in relation to non-MHC restricted cytotoxic activity

Human gamma delta T cell clones having V gamma 9JP and V delta 2DJ1 T cell receptor (TCR) gene rearrangements were isolated form an individual donor and tested for non-MHC restricted cytotoxicity against the B lymphoblastoid cell line, BSM. Most clones were highly cytotoxic but 3/9 clones had very low activity, comparable to that of CD4+ alpha beta T cell clones. Although there was a tendency for clones with low cytotoxic function to produce high levels of interferon-gamma and tumor necrosis factor-alpha, this correlation was not complete. TCR gamma and delta junctional sequences were obtained and were found to be different for all clones. There were no consistent structural differences between gamma delta TCRs of cytotoxic and non-cytotoxic clones, but gamma or delta junctional regions of all three non-cytotoxic clones had unusual features. One clone had a particularly short gamma chain junctional sequence, one had a short delta chain junctional sequence and the third clone was the only one of the panel which failed to utilise the D delta 3 segment. If the gamma delta TCR is involved in target cell recognition in this model of non-MHC restricted killing, such variations in receptor structure may be sufficient to inhibit recognition and thereby reduce the cytotoxic capacity of a minority of V gamma 9+/V delta 2+ clones. Also, a panel of gamma delta T cell clones expressing V gamma 8/V delta 3 isolated from a different donor, were all highly cytotoxic against BSM, indicating that these target cells can be recognised by effector cells expressing a TCR other than the V gamma 9/V delta 2 receptor. The possible influence of other cell surface molecules on non-MHC restricted cytotoxic function is discussed.

T-cell receptor gene expression by human gamma delta T-cell clones from peripheral blood and reproductive tissues in relation to non-MHC-restricted cytotoxic function

T-cell receptor gamma and delta gene expression was determined using V-region-specific monoclonal antibodies in conjunction with Southern blot analysis in panels of gamma delta T-cell clones from human peripheral blood (n = 77) and reproductive tissue (n = 9). Whereas 53 out of 77 (69%) clones from peripheral blood expressed V gamma 9 and V delta 2J1, only 2 out of 9 (22%) from reproductive tissues expressed V delta 2J1. Two out of eight decidual clones expressed both V gamma 9 and V delta 1J1, while this configuration was rare in clones from peripheral blood. The majority of clones from the peripheral blood of one donor expressed V gamma 8 and V delta 3J1. Clones were identified which expressed V delta 1J1 in the disulphide-linked C gamma 1 form of the receptor and which expressed a gene other than V delta 1 in the non-disulphide-linked C gamma 2 form, indicating incomplete concordance between expression of V delta 1 and C gamma 2. V delta 3 could be expressed in the disulphide-linked or non-disulphide-linked form of the receptor. At least 5 out of 77 peripheral clones were expressing V delta genes other than V delta 1, V delta 2, or V delta 3 in conjunction with C gamma 1 or C gamma 2. There was a strong but incomplete correlation between high non-NHC-restricted cytotoxic function and C gamma 1 expression. Clones from the same donor expressing both V gamma 9JPC gamma 1 and V delta 2J1 showed either high or negligible cytotoxicity, and cytotoxic clones expressing C gamma 2 were found. Thus no complete correlation between cytotoxic function and expression of a particular form of the gamma delta heterodimer was identified. The results also suggest that gamma delta T cells from reproductive tissues are less likely to express V delta 2J1 than those from peripheral blood.

CD4-CD8- human T cells: phenotypic heterogeneity and activation requirements of freshly isolated "double-negative" T cells

In the present study we have analyzed the in vitro activation requirements of freshly isolated CD4-CD8- "double-negative" (DN) human peripheral blood T cells. DN cells were isolated from E+ cells by removal of CD4+, CD8+, and CD16+ cells through consecutive steps of C'-mediated lysis and panning. While the majority (79.0 +/- 12.0%) of DN cells were TCR gamma delta+ as shown by staining with mAb TCR delta-1, a minor fraction (6.7 +/- 4.7%) expressed TCR alpha beta as revealed by staining with mAb BMA031. Within the gamma delta+ DN fraction, most cells reacted with mAb Ti gamma A which delineates a V gamma 9JPC gamma 1 epitope, whereas a minor fraction stained with mAb delta TCS-1 which identifies a V delta 1J delta 1 epitope. Functional studies performed at low cell number (1000) per microculture indicated that DN cells can be activated by anti-CD3 mAb, PHA and allogeneic stimulator cells, provided that exogenous growth factors are supplied. Both rIl-2 and rIl-4 acted as efficient growth factors for DN cells, and a synergistic stimulatory effect of rIl-2 and rIl-4 was observed when DN cells were cocultured with allogeneic LCL stimulator cells. As compared to unseparated E+ cells, isolated DN responder cells had a reduced capacity to secrete Il-2 upon PHA stimulation in the presence of LCL feeder cells. The majority of DN cells maintained their CD3+ CD4-CD8- phenotype upon coculture with allogeneic LCL stimulator cells. These data demonstrate that CD3+ DN cells in human peripheral blood are heterogeneous with respect to TCR expression. In addition, they show that freshly isolated DN cells are deficient in Il-2 production but may be normally stimulated by anti-CD3, PHA, or alloantigen if exogenous growth factors (rIL-2 and/or rIl-4) are provided.

T cell receptor gamma gene status of human alpha/beta+ and gamma/delta+ T cell clones: absence of V9JP rearrangements in alpha/beta+ clones is not a result of a lack of rearrangements involving more 5' J gamma segments

T cell receptor (TCR) gamma gene rearrangements were examined in panels of human T cell clones expressing TCR alpha/beta or gamma/delta heterodimers. Over half of the alpha/beta+ clones had both chromosomes rearranged to C gamma 2 but this was the case for only 20% of the gamma/delta+ clones. While more than half of the gamma/delta+ clones showed a V9JP rearrangement, this configuration was absent from all 49 alpha/beta+ clones analysed. However, this was not a result of all rearrangements being to the more 3' J gamma genes as 11 alpha/beta+ clones had rearrangement(s) to JP1, the most 5' J gamma gene segment. Both alpha/beta+ and gamma/delta+ clones showed a similar pattern of V gamma gene usage in rearrangements to J gamma 1 or J gamma 2 with a lower proportion of the more 3' genes being rearranged to J gamma 2 than for the more 5' genes. Several alpha/beta+ and several gamma/delta+ clones had noncoordinate patterns of rearrangement involving both C gamma 1 and C gamma 2. Eleven out of fourteen CD8+ clones tested had both chromosomes rearranged to C gamma 2 whereas all clones derived from CD4-8- cells and having unconventional phenotypes (CD4-8- or CD4+8+) had at least one C gamma 1 rearrangement. Twelve out of twenty-seven CD4+ clones also had this pattern, suggesting that CD4-8+ clones had a tendency to utilize more 3' J gamma gene segments than CD4+ clones. There was some evidence for interdonor variation in the proportions of TCR gamma rearrangements to C gamma 1 or C gamma 2 in alpha/beta+ clones as well as gamma/delta+ clones. The results illustrate the unique nature of the V9JP rearrangement in gamma/delta+ clones and the possible use of a sequential mechanism of TCR gamma gene rearrangements during T cell differentiation is discussed.