Helper signals in the plaque-forming cell response to protein-bound haptens.

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Abstract
The ability of a series of murine T cell hybridomas to deliver an antigen-specific, B cell I-region-restricted helper signal in the generation of specific PFC [plaque-forming cells] resposnes to protein-bound haptens was demonstrated. With some hybridomas the elicitation of optimal PFC responses required the addition of nonspecific factors provided by culture supernatants of concanavalin A-stimulated (Con A SN) spleen cells. Using hapten-primed B cells depleted of T cells and macrophages (MO), a requirement for 3 nonspecific factor preparations to substitute for spleen Con A SN in the elicitation of optimal PFC responses was demonstrated. The 1st preparation was the interleukin l-containing culture supernatant of the MO tumor cell line P388D1, the 2nd with interleukin 2 (IL-2)- and B cell growth factor-containing Con A SN of the T cell hybridoma FS6-14.13, and the 3rd, the .gamma. interferon containing Con A SN of the T cell hybridoma FS7-20.6.18. The P388D1 and FS6-14.13 factor preparations were most effective when added at the initiation of culture; the FS7-20.6.18 factor preparation was most effective when added at 24 h of culture. The activity of FS6-14.13 Con A SN was depleted by incubation with the IL-2-dependent T cell line HT-2. The activity of FS7-20.6.18 Con A SN was abrogated by incubation at pH 2. The generation of PFC respones to protein-bound haptens requires at least 3 nonspecific factors in addition to an antigen/Ia specific helper signal.