Quantitative aspects of the T cell proliferation response to antigen P1 from D. pteronyssinus: suppression by added histamine and limited effects of basophil depletion.

We have recently shown that peripheral blood mononuclear cells from patients sensitive to the house dust mite, D. pteronyssinus, will proliferate in vitro in response to the purified major allergen, antigen P1. Such cell populations, separated on Ficoll gradients, were shown to contain basophils, and had an average histamine content of 12 ng/10(6) cells. Incubation with antigen P1 resulted in the release of histamine, and histamine is known to activate T suppressor cells. In the present experiments we observed up to 80% inhibition of proliferation (mean 50-60%) with histamine added at 3.3 X 10(-7)-3.3 X 10(-5) M. Cultures of T cells supplemented with irradiated non-T cells, that had been depleted of cells bearing surface membrane IgG, IgM and IgE, contained on average 63% less histamine than unseparated cultures. However, no consistent difference in the proliferative response to antigen P1 was observed. Depletion of histamine by pre-incubation of the cells with antigen P1 at 10(-3)-10(-4) micrograms/ml followed by washing of the cells before culture also produced no significant change in the proliferative response. Passage of cell population over nylon wool resulted in depletion of basophils, as well as other cell types, and generally led to a decrease in proliferation. We conclude that release of mediators from basophils in cell cultures does not markedly affect the magnitude of the proliferative response to antigen P1. The varied responses seen with cells from different individuals are likely to reflect differences in the numbers of circulating allergen sensitized T cells.