Transfer of cell-mediated immunity with cell-free leukocyte extracts: III. Demonstration of Ia antigens in the specific component

Abstract

A murine model for Transfer Factor (TF) was used in an attempt to identify the nature of its antigen-specific component. TF was prepared from lymph node cells of CBA/Ca/T6 mice sensitized 30 days previously with 2,4-dinitrofluorobenzene (DNFB). To assay for the specific component of TF, 2 × 10 7 lymphocyte equivalents were injected intravenously into normal syngeneic recipients. Lymph node cells obtained 18–24 hr later gave a positive response in the macrophage migration inhibition (MMI) test in the presence of the soluble analog of DNFB (sodium 2,4-dinitrobenzenesulfonate). The activity of TF was abrogated by absorption with anti-Ia sera including both an Ia alloantiserum (A.TH anti-A.TL) and a xenogeneic rabbit anti-serum which exclusively recognizes carbohydrate-defined Ia antigens. Analysis by paper chromatography using the technique for purification of carbohydrate-defined Ia antigens revealed that MIF production was obtained exclusively with those fractions known to contain Ia antigenic activity. In addition, pretreatment of TF with insoluble conconavalin A (Con A) which has an affinity for carbohydrate-defined Ia antigens resulted in removal of its activity. Taken together these findings pointed to the presence in TF of I-region gene products. Absorption with antibody directed against the dinitrophenyl determinant abolished the capacity of TF to stimulate macrophage inhibition factor production suggesting that it might also contain antigen fragments possibly in association with Ia. No evidence was, however, obtained for H-2 restriction of the action of TF in vivo since it was found to exert an effect in a variety of strain combinations including A.TH and Balb/c which share no known common I-region specificities. Parallel experiments were carried out with the lymphocyte transformation assay since this is known to be a measure of the nonspecific components in TF. Pretreatment with mouse allo-anti-Ia k serum directed against both protein-and carbohydrate-defined Ia antigens caused a partial reduction in the proliferative response. In contrast no change in response was observed when the TF was absorbed with insoluble Con A or anti-DNP serum. Furthermore, lymphocyte transformation was obtained with only one of the three paper chromatography fractions positive in the MMI assay as well as two other different fractions. Taken together, these findings permitted a distinction to be made between specific and nonspecific components of TF and indicated that the specificity of TF could be explained in terms of the presence of I-region gene coded products possibly in association with antigen fragments.