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Soluble, partially purified, histocompatibility antigens that were obtained from the membranes of A/J spleen cells have been assayed for their capacity to elicit immunologic enhancement of two tumors of A-strain origin: YAA-C1 and Sarcoma I. Crude membrane material and a partially purified, soluble antigen that were contained in a specific fraction, obtained after chromatography on a Sephadex G-150 column, elicited enhancement; this fraction has been shown to contain immunogenic histocompatibility-2(a) antigens as well as alloantigenic specificities that were detected serologically. Another soluble fraction did not induce enhancement; this fraction has been shown to contain antigens other than H-2. Passive enhancement of both tumors was achieved with antisera produced in allogeneic mice that were inoculated with crude membrane material or with a fraction obtained by Sephadex G-150 chromatography. These antisera contained cytotoxic and/or hemagglutinating antibodies. Immunologic enhancement was specific. A readily enhanceable tumor, Py 89, of C57BL origin was not enhanced with anti-H-2(a) antisera. These results suggest strongly that all important H-2(a) transplantation antigenic determinants of spleen cells can be recovered by partial papain digestion and fractionation on a Sephadex G-150 column.

Immunological tolerance to a soluble, partially purified fraction of histocompatibility (H)-2(a) antigen was induced in B10.D2 strain mice. The fraction used was obtained after chromatography on a Sephadex G-150 column. Tolerance of humoral-antibody formation (cytotoxins and hemagglutinins) was observed in mice injected with soluble antigen since birth, but cell-mediated immunity, as measured by skin graft survival, remained intact. Tolerance was shown to be specific for H-2(a) antigens, since treated mice produced a regular humoral-antibody response to H-2(b) antigens. These findings, along with previous observations of the immunogenic and enhancing properties of our partially purified fraction, suggest that the solubilized antigen contains all the major determinants of H-2(a) antigens expressed on lymphoid-cell surfaces.

The solubilization and partial purification of mouse transplantation antigens were monitored by (1) an in vitro assay for alloantigenic specificities and (2) an in vivo assay for transplantation antigens controlled by the H-2 histocompatibility locus. Antigens from A/J mice were solubilized by papain and fractionated on a Sephadex G-150 column. The eluate showed a 280 nm absorbance peak (F(1)) in the excluded volume and two peaks (F(2) and F(3)) in the included volume. H-2 specificities 1, 3, 4, 5, 11, 23, and 28 were confined to a single peak in the F(2) fraction. Fractions F(1), F(2), and F(3), were tested for their ability to accelerate skin graft rejection in noncoisogenic strains which differ at both H-2 and non-H-2 loci, and coisogenic strains which differ only at the H-2 locus. All fractions produced significant acceleration of graft rejection in the noncoisogenic strains, but only fraction F(2) produced significant acceleration in the coisogenic strains. These findings indicate that H-2 transplantation antigens detected by our in vivo assay, and H-2 alloantigenic specificities detected by our in vitro assay are solubilized by papain and are eluted in the same peak during Sephadex fractionation.

The amino acid sequences of the lambda chains of two mouse immunoglobulins have been determined. No variations were found between these proteins. The results are compatible with earlier fingerprinting analysis of the two chains, where no differences in the tryptic peptides could be demonstrated. The lack of sequence variations could be the result either of a peculiarly restricted expression of the lambda variable-region genome in the BALB/c myelomas or a small number of germ-line genes involved in the biosynthesis of light chains of the lambda type.