Lymphocytes bearing Fc receptors for IgE. V. Effect of tunicamycin on the formation of IgE-potentiating factor and IgE-suppressive factor by Con A-activated lymphocytes

Attempts were made to induce the formation of soluble factors having affinity for IgE (IgE-binding factors) by activated T cells. Normal rat mesenteric lymph node (MLN) cells were cultured in 1 μg/ml Con A for 48 hr or in 10 μg/ml Con A for 72 hr, and Con A-activated lymphocytes were incubated with rat IgE. It was found that IgE induced an increase in the proportion of Fc(ε)R(+) cells in the Con A-activated cells and formation of IgE-binding factors. However, the nature of IgE-binding factors formed by the cells was different depending on the concentration of Con A for activation. Thus, IgE-binding factors formed by 10 μg/ml Con A-activated cells had a high affinity for lentil lectin and enhanced the IgE-forming cell responses of DNP-OA primed cells. In contrast, the majority of IgE-binding factors formed by 1 μg/ml Con A-activated cells failed to bind to lentil lectin and suppressed the IgE response. Induction of Fc(ε)R by IgE on Con A-activated cells was prevented by tunicamycin, which inhibits protein glycosylation. This antibiotic did not prevent the IgE-induced formation of IgE-binding factors but changed the nature of the factors formed by 10 μg/ml Con A-activated cells. The majority of IgE-binding factors formed in the presence of tunicamycin lacked affinity for lentil lectin and Con A, and suppressed, rather than enhanced, the IgE response. The nature and amount of IgE-binding factors formed by 1 μg/ml Con A-activated cells was not affected by tunicamycin. The results suggest that glycosylation of IgE-binding factors during their biosynthesis is an important step in determining their biologic function.