title: Cognate interactions between helper T cells and B cells. I. Cloning and helper activity of a lymphokine-dependent helper T cell clone (Th-3).
abstract: Two essential events in the development of humoral immune responses to thymus-dependent (TD) antigens are the physical interaction of helper T cells (Th) with B cells and the elaboration of Th-derived lymphokines. Understanding the respective contribution of Th-B cell contact vs. lymphokines in triggering B-cell growth and differentiation has been hindered by the capacity of most Th clones to provide both cell contact-dependent and lymphokine-dependent signals. Our approach to study the role of lymphokines in TD B-cell growth and differentiation was to select antigen-specific Th clones that were able to induce class II-restricted B-cell growth and differentiation only in the presence of exogenously added lymphokines. In such a way, selected Th clones would putatively be defective in lymphokine production, but able to provide cell contact-dependent signals. One clone selected in this manner, Th-3.1, has been instrumental in addressing the role of IL4 in TD B-cell responses. Upon co-culture of purified TNP-specific B cells (TNP-ABC), antigen, and Th-3.1, Th-3.1 was unable to induce TNP-ABC growth or differentiation unless an exogenous lymphokine source (EL4 SN) was provided. The reason for the exogenous lymphokine requirement was two-fold. First, it appeared that Th-3.1 required IL2 to produce lymphokines (IL4) essential for B-cell growth and differentiation. Second, even in the presence of antigen and IL2, the level of lymphokine production by Th-3.1 was insufficient to induce optimal B-cell responses. Because an exogenous source of lymphokines was essential for Th-3.1-induced TNP-ABC growth and differentiation, the requirement for specific lymphokines in TD B-cell responses could be addressed. One lymphokine shown to be necessary for Th-3.1-induced TNP-ABC growth and differentiation was IL4. Addition of anti-IL4 to culture or the depletion of IL4 from the exogenous lymphokine source reduced the TD proliferative and antibody response of TNP-ABC. Because the addition of IL4 alone was unable to restore helper activity, it was concluded that IL4 was necessary but not sufficient for TD B-cell growth and differentiation. Pre-incubation of TNP-ABC and IL4 overcame the IL4 requirement when co-cultured with Th-3.1 and antigen.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Microbiology, Dartmouth Medical School, Hanover, NH 03756.
authors.forename: R J
authors.initials: RJ
authors.lastname: Noelle
authors.forename: J
authors.initials: J
authors.lastname: McCann
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007075:Immunoglobulin M / Q000032:analysis; D007376:Interleukin-2 / Q000378:metabolism; D015847:Interleukin-4; D007378:Interleukins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D008211:Lymphocyte Cooperation; D008222:Lymphokines / Q000494:pharmacology*; D051379:Mice; D008811:Mice, Inbred DBA; D015375:Receptors, Interleukin-2 / Q000276:immunology; D011994:Recombinant Proteins; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
chemical_list: D007075:Immunoglobulin M; D007376:Interleukin-2; D007378:Interleukins; D008222:Lymphokines; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D015847:Interleukin-4