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In previous publications it was shown by avidity measurements, cross-reactivity patterns and genetic analyses, that the tetrapeptide T-T-G-G is the immuno-dominant epitope of the synthetic polypeptide (T, G)-A--L. In the present study this close immunological relationship between the random multichain copolymer (T, G)-A--L and the ordered analogue (T-T-G-G)-A--L is extended by two additional criteria. First, the immune response against (T-T-G-G)-A--L in H-2k nonresponder mouse strains can be reconstituted to high antibody levels by complexing this antigen to methylated bovine serum albumin, as was tested earlier for (T,G)-A--L. The antibodies elicited upon reconstitution in both antigenic systems are directed mainly against the same determinant, T-T-G-G. Second, isoelectric focusing analysis of specific antisera developed with radiolabeled antigen revealed restricted 7 S IgG antibody populations in high responder and reconstituted high and low responder mice. The spectra were found to be of similar complexity in the (T,G)-A--L and in the (T-T-G-G)-A--L system. From these data it was concluded that the repertoires of specific B cells to T-T-G-G are very similar in high and low responder strains, and the defect in the H-2k low responder systems should be located at the level of T-B cell cooperation.

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We have recently reported that various murine T cell clones produce IL-1. Based on this observation we have analyzed in the present study the correlation between the biological functions and the generation of different lymphokines in (T,G)-A--L specific CD4+ clones. One subset of clones--the "helper clones"--were found to provide help to primed B cells, in vitro. These cells could be shown to produce IL-1, IL-2, and B cell stimulatory factor 1 (IL-4) activities and to express mRNA encoding for these three cytokines. The second subset of clones, termed "proliferative clones", were unable to help B cells in vitro but expressed vigorous Ag-dependent proliferations. These cells did not express IL-1, IL-2, or IL-4 activities. They produced another lymphokine(s) which may be granulocyte-macrophage-CSF, or some other factor recognized by the HT2 cell line. This study further substantiates the link between T cell activities and lymphokine repertoire with a special emphasis on the potential role(s) of T cell-derived IL-1.