Shared Idiotypic Determinants on B and T Lymphocytes Reactive Against the Same Antigenic Determinants

Abstract

Normal rat lymphocyte populations house a high percentage of lymphocytes with idiotypic, antigen-binding receptors for the major histocompatibility complex antigens of the rat. These receptors can be isolated from normal serum or lymphocyte supernatants. Idiotypic, antigen-binding molecules released from normal Lewis lymphocytes were isolated using anti(Lewis anti-DA) immunoadsorbents. Analysis by sodium dodecylsulfate [SDS] polyacrylamide electrophoresis using molecules labeled by external or internal means (125I or 3H) demonstrated that B [bone marrow-derived] lymphocytes produce molecules of conventional 7S-8S IgM [immunoglobulin M] type. T [thymus-derived]-lymphocyte-derived molecules had a MW of around 150,000 and consisted of 2 chains of similar size. Such single chains would succumb to proteolysis by normal serum factors to yield fragments in the size range of 30,000-40,000 daltons. All 3 groups of T-cell-derived molecules expressed both antigen-binding and idiotypic markers. No evidence was obtained that any light [L] chains are linked to the T-receptor molecules. Serological analysis of the T-cell molecules failed to prove the existence of any determinants of constant Ig type, nor did these molecules express antigenic markers of major histocompatibility complex types.