PubMed · 62452
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V Vondra, V Vondrová, J Råzicka, V Spicák. 1976. [Provocation tests in respiratory hypersensitivity].. https://pubmed.ncbi.nlm.nih.gov/62452/
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Peripheral T lymphocytes from patients with infectious mononucleosis (IM) are sensitized in vivo against the Epstein-Barr virus (EBV). The expression of HLA-A, B, or C molecules at the target cell surface is necessary for the cytotoxic reaction because (a) EBV-positive Daudi cells lacking HLA-A, B, and C determinants are resistant to anti-EBV T-cell lysis, (b) cytolysis of EBV-positive target cells can be consistently inhibited by anti-HLA-A, B, and C and anti-beta 2 microglobulin antibodies. However, no evidence for allogeneic restriction in this system was apparent as (a) cytotoxic T lymphocytes (CTL) from one given individual could exert a cytotoxicity of a similar magnitude on different EBV-positive target cells, regardless of the number of HLA-A or B specificities shared by the effectors and targets; (b) CTL from IM patients were able to kill target cells without any HLA-A or B antigen in common; and (c) T5-1 variants lacking one or two HLA antigens at the A, B, or D locus are killed to the same extent as the parental cells. 7 of the 9 IM patients with detectable circulating anti-EBV CTL carried the HLA-A1 antigen, whereas none of the 16 IM patients lacking detectable peripheral CTL were HLA-A1 positive (mean specific lysis of T5-1 target cells by T cells from HLA-A1 positive patients: 29.3 vs. 0.6% in HLA-A1-negative patients) (P less than 10(-9)). These data suggest an HLA-A1-linked gene control of the magnitude of the anti-EBV CTL response. Thus, the HLA region appears to act at two different level sin the T-cell-mediated lysis of EBV-infected cells by controlling first, the development of anti-EBV and second, the expression of HLA-A, B, and C molecules involved as recognition structures at the target cell surface.
The nature of Ia antigens which appear on human T cells after activation and the stimuli required for their expression was examined utilizing a monoclonal antibody reactive with the Ia antigen framework. T cells were purified using monoclonal antibodies directed either at the entire T-cell population (OKT3) or the T-cell inducer subset (OKT4). By indirect immunofluorescence, it was shown that the human T-cell population contains no detectable Ia+ cells in the resting state. In contrast, in excess of 60% of the T-cell population expresses Ia antigen after alloactivation in the mixed lymphocyte culture. Moreover, these Ia antigens are expressed within both the OKT4+ and OKT4- subsets. Similarly, phytohemagglutinin and concanavalin A induced approximately 20% of peripheral T cells to express Ia antigen and the expression of these antigens is not restricted to either OKT4 subset. In contrast, only the inducer T-cell population which proliferates maximally to soluble antigen expresses Ia antigens after activation by tetanus toxoid. Thus, the expression of human Ia antigens on unique T-cell subsets depends upon the activation stimuli utilized and ability of the individual subset to respond to a given stimulus. Additional studies indicated that Ia antigens appear on previously Ia- T cells after activation and do not result from clonal expansion of a small subset of Ia+ T cells.
The kinetics of the antigen-antibody reaction were examined systematically in four kinds of double-antibody radioimmunoassay (RIA). In all the RIAs, the dose-response curves obtained on delayed addition by 24 to 48 h of labeled antigens (curves B), were shifted downwards and to the left of those obtained on simultaneous addition of the reagents (curves A), resulting in improved sensitivity of the assay. On the contrary, the dose-response curves obtained on delayed addition of unlabeled antigens (curves C), were shifted upwards and to the right of curves A, resulting in reduced sensitivity. In human thyrotropin (hTSH) RIA, curves B and C approached curves A very little, even after 168 h of incubation. A similar phenomenon was observed with anti-hTSH antisera from five different sources at two incubation temperatures, and the dilution curves of 125I-labeled hTSH and unlabeled hTSH appeared to be parallel. Therefore, the phenomenon observed with hTSH RIA could not be attributed to the assay conditions or to peculiar properties of the reagents used. In insulin RIA, the reversibilities of the shifts of curves B and C were slight but comparable to those observed in hTSH RIA. In 1-3,5,3'-triiodothyronine RIA, curves B and C gradually approached curves A on prolonged incubation and curves B became nearly identical with curves A after 98 h of incubation. On the other hand, in alpha-fetoprotein (AFP) RIA, curves B and C did not approach curves A, even on prolonged incubation for up to 288 h. The "equilibrium affinity constants" of the antibodies were of the same order of magnitude, thus it is unlikely that differences in the constants can account for the differences in the reversibility of these RIAs. In APF RIA, a significant amount of the antigen-antibody complex was precipitated without second antibody after centrifugation at 3000 X g. These findings suggest that the extent of dissociation of the immune complexes depends on their size, which in turn is related to the molecular weight of the antigen.