Separate cytotoxic T lymphocyte subsets recognize the different H-2 specificities.

Using a monolayer adsorption technique, the fine specificity of cytotoxic effector T lymphocytes (CTL) generated against allogeneic or semi-allogeneic H-2 haplotypes was investigated. The results show that: (a) CTL reacting with the private specificity expressed on an H-2.K molecule can be separated from those reacting with the public specificities expressed on the same molecule and (b) the CTL that recognize cross-reacting H-2 determinants (public specificities) can also be separated into several subpopulations. These data support the hypothesis that an allogeneic stimulation induces a large number of independent T cell clones that react with H-2 determinants.

Alien H-2 Antigens on a Chemically Induced Fibrosarcoma: Further Evidence in Crude Membrane and Soluble Extracts of the Tumor

Crude membranes (CM) were obtained from in vivo subcutaneous nodules of the methylcholanthrene-incuded BALB/c fibrosarcoma C-1 by forcing tumor fragments through a mechanical press and subsequent differential centrifugation. This immunogenic tumor has been previously shown to express both H-2d and extra H-2k-like antigens. Original H-2d and alien H-2k antigenic activities were present in CM C-1 as judged by the specific inhibition of the C'-dependent cytotoxicity of monospecific H-2 alloantisera on normal 51Cr-labelled lymphoid cells. Both K- and D-end private H-2d antigens (31 and 4), and H-2d public antigens 8, 29, 35 were detected in CM C-1. In addition, the alien H-2Kk.23 private specificity and the public H-2k.1, 5, and 25 were also found in CM C-1. A weak but reproducible activity attributable to the Dk private antigen 32 was also revealed in this material. A hierarchy in the expression of both H-2d and H-2k specificities was evident in CM C-1 which paralleled, although with an overall lower antigenic activity, those of two other BALB/c (H-2d) fibrosarcomas and of a C3Hf (H-2k) lymphoma, respectively. CM from normal BALB/c and C3Hf spleens, while expressing higher amounts of all the tested H-2 antigens, displayed a hierarchy of the different specificities similar to that of neoplastic tissues. Crude soluble (CS) material was obtained from CM C-1 by deoxycholate treatment and was tested in the inhibition assay for the presence of H-2d and alien H-2k antigens. Only specificities with the highest expression in CM were found in CS, i.e. H-2.4 and 29 for H-2d and H-2.25 for H-2*. Both CM and CS from C-1, but not from another control BALB/c sarcoma, were able to significantly inhibit the activity of an oligospecific serum to the Kk-coded antigens.

Cytotoxic T-cell responses show more restricted specificity for self than for non-self H-2D-coded antigens

The specificity of recognition of H-2 antigens by various subsets of Tc cells was investigated with respect to the two separate molecules known to be coded in the H-2D(d) region (a) D which carries the private specificity H-2.4 and (b) D' which carries the public specificity H-2.28. BALB/c.H-2(db) mutant mice express D but not D' on their cell surfaces, whereas wild-type BALB/c mice express both D and D'. H-2 restricted Tc cells specific for viral-plus- H-2D(d)-coded antigens on infected self cells, or minor H-plus-H-2D(d)-coded antigens on H-2-compatible cells apparently recognize D, but do not detectably recognize D. In contrast, BALB/c-H-2(db) anti-BALB/c Tc cell responses do recognize D' (the only known antigen which is not shared by mutant and wild-type); furthermore, D' is also detectably recognized by a significant proportion of the Tc cells that respond in MLR to H-2D(d)-coded antigens. In these latter responses, D' was recognized separately from D, i.e., the response was not "H-2 restricted". These results indicate that H-2 restricted Tc cell responses to modified-self cells are more specific for self H-2D(d)-coded antigens then are allogeneic Tc cell responses directed at the same antigens, in that haplotype-unique (private) specificity recognition (of the D molecule) exclusively occurs only in the former, not the latter case. The implications of this specificity of H-2 restricted responses for possible processes of somatic selection of anti-self recognition structures on progenitor Tc cells are briefly discussed.

Private specificities of H-2K and H-2D loci as possible selective targets for effector lymphocytes in cell-mediated immunity.

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.