The lymphocyte stimulation test: a sensitive technique for the detection of circulating platelet antibodies.

Platelet autoantibodies are unable to react in standard immunological reactions and this makes it difficult to detect their presence in the serum. The present work shows that peripheral blood lymphocytes from normal donors are stimulated in vitro by autologous platelets sensitized with sera from patients with different types of chronic thrombocytopenia. Comparison of the lymphocyte stimulation test with the platelet factor 3 (PF3) availability assay and the serotonin (5HT) release test demonstrated that the former method was the more sensitive one. Some sera from patients with SLE and thrombocytopenia also induced both a slight lymphocyte stimulation in the absence of platelets and a complement-dependent release of serotonin, probably due to the presence of immune complexes.