Characterization of antigen-binding molecules from T suppressor hybridomas

Distinctive molecular markers and biological activities in two tumour-specific murine T suppressor factors

Murine suppressor factors (SF) in tumour-bearer serum (TBS) and tumour-bearer spleen cell culture supernatants (SCCS) were compared with regard to their molecular markers, cellular requirements and suppressive activities. Suppressor factors in SCCS bear the idiotype I-J, and markers recognized by B16G and anti-lipomodulin antibodies require Ly2+ I-J+ cells for their production and cells of the same phenotypes, for suppression to be manifested in leucocyte adherence inhibition (LAI) assays, are not immunoglobulin (Igh)-restricted and are active in both the afferent and efferent phases of the immune response. Suppressor factors from TBS resemble those from SCCS with regard to idiotype, I-J and lipomodulin-like markers, but in contrast, do not bind to B16G antibody, require Ly2+ but not I-J+ cells for suppression to be manifested in LAI assays, are Igh-restricted, and suppress delayed-type hypersensitivity (DTH) reactions only when injected in the afferent phase. These results show that the SF from the different sources in tumour-bearing mice are not identical; they may be different parts of a suppressor cascade, or they may belong to entirely separate suppressor cascades.

A monoclonal antigen-binding T cell immunoprotein: antigenic relatedness to T cell receptor beta chain FR1 V and J peptide segments: physicochemical distinctiveness from classical immunoglobulins and T cell receptor heterodimers

The monoclonal murine T cell hybridoma, 51H7D, was previously shown to bind the arsazobenzene hapten and to produce a soluble antigen-binding molecule. In this paper we characterize this antigen-binding immunoprotein for its relationship to known T cell receptors serologically, using antibodies specific for variable region framework, or joining region peptides predicted from gene sequence and by biochemical means. The 51H7D cell expresses a protein with subunit size of approximately 31,000, that reacts antigenically with affinity-purified antibodies directed against synthetic first framework and joining segment peptides, corresponding to the gene sequence of the T cell receptor beta chain, YT35. This molecule does not react with affinity-purified antibodies directed against murine immunoglobulin, framework 1 sequences of alpha and gamma T cell receptors, or with antibodies against synthetic heavy chain joining segments. The subunit of mol. wt. 31,000 can form higher aggregates, notably in the mol. wt range of 60,000-70,000, depending upon extraction conditions. The soluble form of the antigen-binding molecule bears the J beta cross-reactive determinant and occurs predominantly as a charge restricted molecular species of approximate mol. wt 60,000-70,000. The purified molecule has a blocked N-terminus, but quantitative statistical analysis of its amino acid composition indicates a closer relatedness to T cell receptor beta chains and other antigen-binding T cell products, than it has to alpha, gamma or delta TCR chains. No evidence for more than one type of polypeptide chain was found and the polymerization is not dependent upon the formation of disulfide bonds. These studies raise the possibility that antigen-binding soluble T cell molecules might belong to a new family of immunoproteins, that is related to, but distinct from, classical immunoglobulins and alpha beta or gamma delta heterodimers.