Isolated hapten‐binding receptors of sensitized lymphocytes. IV. Expression of immimoglobulin variable regions in (4‐hydroxy‐3‐nitrophenyl) acetyl (NP)‐specific receptors isolated from murine B and T lymphocytes

Primary anti‐NP [(4‐hydroxy‐3‐nitrophenyl)acetyl] antibodies and NP‐specific receptors isolated from T cells of mice carrying the Ig‐1^b allotype express the NP^b idio‐type and a fine specificity marker (heteroclicity) which are both controlled by V genes in the heavy chain linkage group. While in antibodies both markers are invariably expressed in association with Ig light chains of the Λ type, antigen‐binding T cell‐derived receptors appear not to follow this rule in that they do not significantly bind to anti‐Λ antisera. Mice of the SJL strain also carry the Ig‐l^b allotype but express a defect in Λ chain synthesis, and their primary anti‐NP response is thus almost completely devoid of Λ‐bearing heteroclitic molecules of the NP^b idiotype. In contrast, both NP^b idiotype and heteroclicity are expressed in the majority of T cell‐derived receptors. This result permits a positive discrimination between T cell‐derived receptors and humoral antibodies in the SJL strain and shows that V gene expression follows different rules in the T and the B cell compartment. The expression of Ig V regions in isolated T cell‐derived receptors was also analyzed with antisera binding to presumed “framework” determinants of the V_H and the V_Λdomains of Ig. A reaction of anti‐V_H antiserum with isolated T cell receptors could clearly be demonstrated. The anti‐V_Λ antiserum may bind to a minor fraction of the NP‐specific molecules in our T cell receptor preparations.