Muneo Takaoki

The role of the epitope density and cross-reactivity between two different purine nucleosides coupled to cells☆

Cellular immune responses against nucleic acid antigens were analyzed in BALB/C mice. Delayed-type hypersensitivity (DTH) could be elicited by immunizing and challenging with either guanosine-coupled spleen cells (G-SC) or adenosine-coupled spleen cells (A-SC), and measured by footpad swellings. The epitope density was critical for immunization. This cellular reaction was specific to nucleosides, and cross-immunity was observed between A-SC and G-SC. In addition, cross-unresponsiveness was observed between these two nucleosides. In contrast, soluble carrier proteins coupled with either guanosine or adenosine did not induce cross-reactive immunity or unresponsiveness. The significance of the difference between these two forms of antigens in the ability to induce cross-reactivity is discussed in the context of T versus B-cell recognition in the induction or the expression of the immune response.

ANTIGEN‐PRESENTING CELLS IN IMMUNITY AND SUPPRESSION

It is well documented that the route of administration of antigen influences whether immunity or suppression is induced. It was observed that the intravenous route of administration of ligand-coupled cells activales the suppressor pathway, while the subcutaneous administration of ligand-coupled cells activates the helper pathway. This suggests different modes of antigen presentation for the two routes. We have evaluated the role of specialized antigen-presenting cells (APC) in the induction of T cell immunity in vitro. By using the bovine serum albumin flotation method, we have been able to isolate a potent APC source for the generation of primary and secondary cytolytic responses to azobenzene arsonate (ABA)-coupled cells in vitro. This APC population, which can turn on the helper circuit, has the following characteristics: low density, 1500 rad x-ray resistance, uv sensitivity, and I-A+. In in vivo studies, we observed that uv-treated mice inoculated with uvtreated hapten-coupled APC developed a population of hapten-specific suppressor T cells capable, upon adoptive transfer, of inhibiting the generation of T cell immunity in normal mice. This suggests the possibility that, in the absence of I-A+ APC, special uvresistant presenting cells capable of activating certain suppressor cells remain or certain subsets of suppressor cells are activated in the absence of any APC. In order to clarify this, we developed a suppressor factor-sensitive killer cell generation system. We observed that the so-called first-order suppressor factor secreted by hybrid cells can suppress the secondary ABA killer generation.

REGULATION OF THE IMMUNE RESPONSE TO CELL SURFACE ANTIGENS

ABSTRACT Regulation of immune responses to the hapten azobenzenearsonate involves Lyt 1 + 2 − T cells in the induction of cell-mediated immunity and at least three subsets of suppressor T cells in the suppression of immunity. Suppression is regulated through a series of idiotype-anti-idiotype and I-J mediated events. Lyt 1 + 2 − T cells also play a critical role in the induction of immunity in the S1509a fibrosarcoma. Suppression in this system is mediated through at least two sets of suppressor T cells and can be enhanced or inhibited by alloantiserum directed at I-A or I-J gene products. In vitro suppression of mouse myeloma antibody production can be mediated by two subsets of anti-idiotype suppressor T cells or by cytotoxic T lymphocytes. Regulation of myeloma by the suppressor cells and its potential clinical importance are discussed.

GENERATION OF GENETIC RESTRICTIONS IN THE SUPPRESSION OF DELAYED‐TYPE HYPERSENSITIVITY

A soluble suppressor factor (TsF,) produced by first-order suppressor T cells in the azobenzene arsonate ( ABA) -specific delayed-type hypersensitivity (DTH) reaction bears crossreactive idiotypic (CRI) determinants of anti-ABA antibodies and determinants encoded in the I-J subregion of the H-2 gene complex. TsF,, when injected i.v. into naive mice, induces second-order suppressor T cells that produce a soluble suppressor factor, TsF,. TsF, suppresses the effector phase of DTH and can bind to CRI. TsF, can also be induced in a CRIstrain by injecting CRI-coupled spleen cells, but such TsF, works only in CRI+ (V, restriction) and H-2 matched (H-2 restriction) strains.l To investigate how these restrictions are generated, either TsF, extracted from spleen cells of A/J(H-2a, CRI+) mice or monoclonal TsF, produced by F12, a suppressor T cell hybridoma line of A/J origin,* was injected i.v. into various strains of mice daily for five days. TsF, were extracted from the spleen cells of these mice by freezing and thawing on day 7 after the first injection. Mice were injected i.v. with TsF2 on days 4 and 5 after S.C. immunization with ABA-coupled syngeneic spleen cells and challenged into the hind footpad with ABA solution on day 5. The footpad response was measured 24 h later. TsF, of A/J mice suppressed only A/J DTH. TsF, induced by A.By (H-2h, CRIt) mice suppressed A.By DTH, but not A/J DTH, despite the fact that A/J TsF, was used for its induction. Similarly, TsF, induced in C57BL/6 (H-2b, CRI-) mice suppressed A.By DTH, but not A / J DTH. To do intra H-2 mapping of the restriction, TsF, were raised in BlO.A(3R) (bbbbkdd) and BlO.A(SR) (bbbkkdd), and tested in A/J and A.By. TsF, of BIO.A(3R) suppressed A.By DTH but not A/J DTH, while TsF, of BlO.A(5R) suppressed A/J DTH but not A.By DTH. It was concluded that the H-2 restriction was determined by the I-J subregion of the H-2 complex of the mice that produce TsF,. It may reiate to recognition of 1-3 determinants by a subset of suppressor cells. I-J determinants expressed on TsF,, however, did not seem to play a role in the determination of the restriction. On the other hand, VII restriction may be generated by the recognition of the CRI determinants of the TsF, molecule.