Disordered immune homeostasis in chronic idiopathic thrombocytopenic purpura.

A T:B co-culture system was used to test for the presence of disordered immune homeostasis in the autoimmune disease, chronic idiopathic thrombocytopenic purpura (ITP). Various numbers of T cells were added to a fixed number of B cells in the presence or absence of the polyclonal activator, pokeweed mitogen, and IgG production measured in the culture supernatants 6 days later. The results demonstrated a defect in T cell-dependent suppression and/or a state of B cell hyper-responsiveness in lymphocytes from patients compared to normal controls. The loss of T cell-dependent suppression could not be readily explained in terms of the therapy being used nor by the presence of circulating IgG containing immune complexes. The findings of a similar abnormality in some cases of non-immune thrombocytopenia suggested that the reduction in suppression observed in chronic ITP was unlikely to be a primary event in disease pathogenesis, although it could well contribute to the ongoing autoimmune response.