Analysis of T cell-replacing factor-like activity: potent induction of T helper activity for human B cells by residual concanavalin A and interleukin 2.
At least two factors with the capacity to induce IgM synthesis in human B cells were found to be present in the 15-20-kDa fraction of the supernatant of mononuclear cells activated with concanavalin A (Con A) and phorbol ester. Previously, it has been shown (Sauerwein, R. W. et al., Eur. J. Immunol. 1985. 15: 611) that interleukin 2 (IL2) in this material is able to induce T cell-dependent IgM secretion in normal B cells. Evidence was obtained for the presence of another factor distinct from IL2 that could replace T cells in the induction of B cell differentiation. We have analyzed this factor with the use of a neoplastic B cell population of prolymphocytic origin that was functionally nonresponsive to IL2. T cell-replacing factor (TRF)-like activity and IL2 could be separated by ion-exchange chromatography, although a small amount of IL2 was recovered in the TRF fractions. This small amount of IL2 was found to be crucial for the observed TRF activity. Moreover, a substantial amount of monomeric Con A was detected in the TRF preparation. Our studies show that Con A in the presence of IL2 can act as a potent inducer of helper function in lower numbers of T cells for normal and neoplastic B cells. Functional assays for T cell contamination in B cell suspensions are therefore of limited value because they are determined by the efficiency of the stimulating signal. Particularly in those B cell factor preparations, obtained from mitogen-activated T cells with an obligatory or unidentified role of IL2, the possible effect of a contaminating mitogen must be considered.
D000917:Antibody Formation / Q000187:drug effects; D001402:B-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology*; D003470:Culture Media; D006801:Humans; D007075:Immunoglobulin M / Q000378:metabolism; D007376:Interleukin-2 / Q000494:pharmacology*; D015848:Interleukin-5; D008211:Lymphocyte Cooperation / Q000187:drug effects*; D008222:Lymphokines / Q000302:isolation & purification / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
D003470:Culture Media; D007075:Immunoglobulin M; D007376:Interleukin-2; D015848:Interleukin-5; D008222:Lymphokines; D003208:Concanavalin A