Receptors of effector T lymphocytes of congeneic strains of mice do not recognize public H-2 specificities and react to private H-2 specificities only. This has been established with the use of three tests: direct cytotoxicity assay of immune lymphocytes upon target cells, specific absorption of the lymphocytes on the target cells, and rejection of skin grafts at an accelerated fashion. Immunization with two private H-2 specificities in the system C57BL/10ScSn leads to B10.D2 induces formation of two corresponding populations of effector lymphocytes in unequal proportion: a greater part of them is directed against the private specificity H-2.33 (Kb), while the smaller part is towards H-2.2 (Db) private specificity. These two populations of effector lymphocytes do not overlap, as demonstrated by experiments on their cross-absorption on B10.D2 (R107), B10.D2 (R101), B10.A(2R), and B10.A(5R) target cells, as well as on mixtures of R107 and R101 targets. Following removal of lymphocytes reacting with one of the private H-2 specificities, lymphocytes specific to the other specificity are fully maintained. A mixture of target cells, each bearing one of the two immunizing private specificities, absorbs 100% of the immune lymphocytes and is totally destroyed by them. It is suggested that H-2 antigens are natural complexes of hapten-carrier type, in which the role of hapten is played by public H-2 specifities and that of the carrier determinant by either private H-2 specificities or structures closely linked to them. Various models of steric arrangement of MHC determinants recognized by receptors of effector T lymphocytes are discussed.

No abstract

No abstract

The technique o f elution b y pronase of murine immune lymph node cells adherent to relevant allogeneic target cells has been developed for enrichment of effector T cell population. A fraction of killer cells has been obtained possessing cytotoxic activity which exceeds that of the initial immune lymphocyte population b y a factor of 6-8 as judged by a number of lymphocytes required for 50 % cytotoxic effect (CE). T h e gain in CE is fairly reproducible in different H-2 systems and under various lymphocyte-target incubation conditions. It appears to be due t o the quantitative enrichment of the population in cells bearing receptors to the particular H-2 antigens and giving rise to specific CE rather than t o an increase in cytotoxic activity per cell resulting from treatment with the target monolayer and pronase. The eluted killer cell fraction is characterized by a twofold increase in percentage of cells killed by anti-@ antibody, a 4-5-fold increase in the number of DNA-synthesizing cells and b y an increase in medium and largc lymphocyte content. A further enrichment in effector lymphocytes is reached by depletion of B cells a t the expense of their receptors t o Fc fragment of Ig. Macrophage monolayer fixed by glutaraldehyde lost its capacity t o absorb effector lymphocytes. T h e implications of the data obtained for further studies o n cell-mediated immunity are discussed. 1 I ] and the rosetteHowever, one should not disregard the possibility that in all the above-mentioned cases passive absorption of Ig on the T cell surface is revealed rather than its true (endogenic) receptors. In fact, receptors to both F c fragment of IgM Label release upon incubation with immune and normal lymphocytes EA: Erythrocytes-antibodies 281 the possibility is not excluded that such antibodies are actually produced by small B cell contaminants present in suspension. Experimental analysis [29, 301 of these and other ambiguous points in the interpretation of such results have raised doubts whether the above cited reports really concern the endogenic T receptors. .Introduction'Meanwhile, T cell receptors responsible for interaction with target cells (TC) in the H-2 system have been shown to differ from Ig of the known classes [31-331. Such receptors are manifested in the ability of cytotoxic lymphocytes t o get selectively attached for several hours at 25-37 OC t o the naturally immunosorbent-monolayer of the relevant TC ' [34-361. To study the properties o f the effector T cells, including the nature of their receptors specific to the H-2 antigens, it seems t o be essential t o isolate these cells from the whole population where they occur in a ratio of 1-4 ' %, [ 3 7 -~3 9 ] , and to concentrate them.The present work describes a technique developed for the enrichment of the effector T lymphocyte population in cells reactive to the particular H-2 antigens. T h e ability of pronase to completely and reversibly prevent immune lymphocytes from absorption on T C monolayer with no damage of the latter described earlier [40] is t...

No abstract

Specific suppressor T cells (SSTC), primed in vivo with H-2 antigens, have been shown previously to inhibit DNA synthesis in the one-way, three-cell mixed lymphocyte reaction (MLR) provided that (a) the stimulator cells bear the priming H-2 antigens, and (b) the responder cells possess IC + S regions homologous to those of the SSTC. Anti-B10.A B10.A(2R) SSTC (anti-Dd) and anti-A.AL A.TL SSTC (anti-Kk) are shown here to be able to inhibit the DNA synthesis triggered in MLR, not only by the corresponding antigens, Dd and Kk, respectively, but also by irrelevant, third-party H-2 and Mls products provided that the corresponding and third-party antigens are presented on the same stimulator cell. If stimulator H-2 regions, whose products interact with SSTC and responders, are located on different stimulator cells within the particular MLR, SSTC activity is not elicited. Participation of cytotoxic T lymphocytes in DNA-synthesis suppression is ruled out. Direct contact or location of the inhibited responder cell very close to SSTC is considered to be required for the development of SSTC activity.

No abstract

The MC-resistant specific suppressor T cells that inhibit DNA synthesis and CTL generation in MLC were induced in vivo by gamma-irradiated allogeneic lymphoid cells in a large dose. MLRs were inhibited only slightly when triggered by third-party cells, even neighbouring with the corresponding stimulators. Unlike the irradiated cells, intact allogeneic lymphoid cells induced a mixture of macrophage-like and T-cell suppressors with a pronounced non-specific component of the action. Syngeneic cells induced low active non-specific suppressors of macrophage type only. The suppression was not due to a cytotoxic effect, since specific T suppressors differed from CTL by conditions of induction and high sensitivity to gamma-irradiation and from CTL precursors by high sensitivity to CY and HC. The specific T-suppressors could be selectively removed by adherence to a macrophage monolayer of the corresponding donor. The subsequent elution of adherent lymphocytes with pronase resulted in enrichment of specific T suppressors by a factor of 30 and 2.6, as judged by reduction in the number of lymphocytes required for 50% inhibition of DNA synthesis and 33% inhibition of CTL generation, respectively. The high specificity of this enrichment is shown by using both syngeneic monolayers for fractionation and third-party stimulators in MLR for testing and by disappearance of slight non-specific suppression caused by non-fractionated suppression. Complete inactivation of the eluted suppressors with anti-Thy-1.2 and anti-T antibodies, their resistance to anti-Mls antibodies, carrageenin, and carbonyl iron, together with the data of autoradiographic study and total DNA synthesis in the population indicate that the eluted highly specific suppressors represent mainly DNA-synthesizing large and medium T lymphocytes.