The immunoglobulin-like T-cell receptor. II. Codistribution of Fab determinants and antigen on the surface of antigen-binding lymphocytes of mouse thymus

Surface expression and partial characterization of an arsonate hapten-specific idiotype-bearing T-cell receptor

Anti-idiotype antibodies raised against the arsonate hapten idiotype have been used to detect arsonate-binding receptors on the surface of peripheral T cells of A/J mice and to isolate this material after biosynthetic labeling for partial chemical characterization. It was found that 2-3% of splenic T cells from arsonate-immune mice specifically bound the hapten using immunofluorescent keyhole limpet hemocyanin as a carrier. In double-immunofluorescence labeling experiments, a high proportion (approximately equal to 70%) of these cells also bound the (Fab')2 fragment of rabbit anti-idiotype antibody in exactly the same patches on the cell as the arsonate hemocyanin antigen. In addition, the anti-idiotype antibody inhibited the binding of the hapten-carrier complex to T cells by approximately equal to 70%. In parallel experiments, fowl antibodies against mouse (Fab')2 fragments bound to 100% of arsonate-binding T cells in the same cell-surface patches as the hapten, and were capable of inhibiting 100% of the hapten-binding cells. Capping, shedding, and resynthesis experiments indicated that the T cells synthesized their antigen-binding idiotype-bearing receptors. Immunoblots of unreduced detergent extracts of purified splenic T cells developed with anti-idiotype antibodies showed bands at 150,000 and 94,000 Da. Equal amounts of protein extracted from liver and analyzed in the same gels as the T-cell material failed to show any reactivity with anti-idiotype antibodies. To confirm the biosynthetic origin of the idiotype-positive materials, detergent extracts from 75Se-methionine- or [3H]leucine-labeled Con A-treated splenic T cells were reacted with anti-idiotype antibodies and the bound material was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the presence of 2-mercaptoethanol the major band was at 68,000 Da, with variable minor levels of material at 45,000 Da, while when hapten was used to isolate the receptor a dominant 25,000- to 30,000-Da band was seen. We believe that the higher-molecular-weight materials are multimers of the 25,000-30,000 subunit.

Antigen binding to lymphoid cells from unimmunized mice. VI. Specificity of purified multiple antigen-binding cells

In order to determine the specificity of antigen binding by double antigen-binding lymphocytes obtained from mouse bone marrow and spleen, three types of experiments were performed (1) a high excess of unlabelled antigen was tested for its ability to inhibit the binding of unrelated antigen to both single and double antigen-binding cells; (2) polyvalent anti-mouse immunoglobulin was assessed for its ability to inhibit antigen binding; and (3) the ability of one antigen to co-cap (or codistribute) with either another antigen or anti-immunoglobulin was studied to determine the spatial relationship of these components on the cell membrane. In order to study an adequate number of double ABC, these cells were enriched by using NIP-specific ABC as a starting population. The data indicate that double antigen binding occurs via independent immunoglobulin cell surface receptors which can be spatially separated from one another under appropriate capping conditions.