Requirement for the location of both appropriate and irrelevant H-2 antigens on the same stimulator cell for unspecific DNA-synthesis inhibition by the H-2-antigen-primed, specific suppressor T cells

Intravenous injection of allogeneic cells can prime T-lymphocytes with cytotoxic activity

The possibility of specific cytotoxic T-lymphocyte (CTL)2 induction was shown upon intravenous (i.v.) immunization of mice with 9 x 10(7) irradiated (2000 rad) allogeneic splenocytes. The induced CTL express the cell surface markers Thy1.2+, L3T4- and Lyt2+. No correlation between the level of cytotoxic activity and the ability to inhibit proliferation was shown in populations of lymphocytes, primed both by i.v. immunization and in mixed lymphocyte culture (MLC). The possible role of cytotoxic activity in down-regulation of the immune response is discussed.

Regulatory mechanisms in cytotoxic T lymphocyte development. III. Induction, specificity, and genetic restriction of an in vitro suppressor T cell

We addressed questions pertaining to the immunogenetics of an in vitro alloinduced suppressor T cell (Ts) previously shown to inhibit cytotoxic T-lymphocyte (CTL) development by suppressing CTL precursor proliferation. Using intra-MHC recombinant strains of B10 congenic mice, the requirements for H-2 differences to induce Ts activity, the antigen specificity of the Ts, and the genetic restriction of Ts function were studied. It was found that differences at the K, D, or I regions alone can induce strong suppressor activity. Suppression of CTL development does not appear to be genetically restricted since the Ts inhibit CTL from responder cells disparate at K, K and D, I, or K and I. The alloinduced Ts is specific for the antigen stimulating its induction, but also inhibits CTL responses against immunologically unrelated determinants, even between class I and class II antigens, provided those determinants are carried on cells expressing the original inducing antigen. Ts can be triggered by antigens present on the responder cells but absent on the stimulator cells, indicating that the suppressive signal may be exerted directly on the responder population without specific interaction with stimulator cells.

Suppression of the cytotoxic T cell response to minor alloantigens in vivo. Linked recognition by suppressor T cells

This report describes the activity of transferable suppressor T cells (Ts) generated in vivo in response to minor alloantigens. These Ts cells are antigen specific in both primary and secondary in vivo cytotoxic T lymphocyte responses to minor alloantigens and are the result of a host response rather than of a graft-vs.-host reaction. The Ts cells are produced soon after immunization and their activity is transient. They act via "linked recognition", since they can suppress the cytotoxic T lymphocyte response to noncross-reactive minor antigens, but only if these are presented on the same antigenic cell. A model for dominant low responsiveness in (high X low responder)F1 animals is proposed, whereby Ts cells, activated via the low responder allele, work by linked recognition to suppress helper cells activated via the high responder allele.

Inactivation of specific anti-H-2 suppressor T cells by antisera to I-J and I-C subregion products of the H-2 complex

Two antisera to Ia antigens, products of the H-2 complex I-Cd and I-JkEk subregions, respectively, have been obtained by immunization of the F1 hybrids of recombinant strains of mice. These antisera are shown to display a 50% cytotoxic effect in vitro, in the presence of complement, upon lymphocyte populations immune to the H-2-complex antigens and enriched for specific suppressor T cells (SSTC) by fractionation on a monolayer of target cells. The specificity of anti-Ia cytotoxins is shown by cross-antibody absorption with T and B cells of mice originating from the recombinant H-2 haplotypes and bearing either particular I-Cd, I-Jk and I-Ek antigens, or their combinations. Anti-I-Cd cytotoxins were found to react with both B and T cells, but at a different rate, and the anti-I-JkEk serum contains two antibody types directed to I-Ek and I-Jk products, respectively, the latter being able to react preferently with T cells. Although both antisera do inactivate the in vitro SSTC function in the presence of complement to a similar degree, the inactivating action of the anti-I-Cd serum, but not that of the anti-I-JkEk serum, occurs without complement. SSTC are shown to bear both Ia-antigens, I-J and I-C, as shown by both inactivation of the anti-suppressor effect of the antisera absorbed with spleen cells of different H-2 origin, and variation of the H-2 origin of SSTC pretreated with the intact antisera. It is suggested that these two markers, located on the same SSTC, function differently in SSTC immune to the H-2 antigens, and I-C antigen expression on the SSTC surface is presumed to be required for their interaction with the inhibited responder T cells proliferating in MLC.

Haplotype-specific suppressor T cells mediating linked suppression of immune responses elicited by third-party H-2 alloantigens

Specific suppressor T cells (Ts) were induced in vitro by incubation of mouse spleen/lymph node cells with allogeneic heat-treated cells. These Ts inhibit mixed lymphocyte reaction (MLR) in a haplotype-specific manner. Ts also suppress cell proliferation induced by third-party H-2 alloantigens provided these are expressed on the same cell surface as at least some of the H-2 antigens used for Ts activation. Ts activated by H-2 plus non-H-2 alloantigens suppress an MLR induced by irrelevant H-2 alloantigens if these are expressed on the same cell surface as the non-H-2 alloantigens used for Ts activation. Products of the H-2 region or non-H-2 alloantigens which are not able to stimulate cell proliferation do not activate Ts. These Ts are first demonstrable after 4 days of incubation of lymphoid cells with heat-treated allogeneic cells and they inhibit MLR only if added at the very beginning of the culture. Exogenous interleukin 2 does not overcome suppression and the suppression is not due to a cytotoxic effect, since heat-treated cells do not elicit cell proliferation or cytotoxic cells. Moreover, the specific Ts differ in their Thy-1+,Ly-1+,2-phenotype from Ly-2+ allospecific cytotoxic cells. Thus specific Ts could be induced in vitro, which demonstrate linked suppression for third-party H-2 alloantigens provided these are expressed on the same cell surface as the antigens used for Ts activation.