Transient disappearance of immunologic disorders and remission after intercurrent measles infections in children with chronic idiopathic thrombocytopenic purpura.

In two children with chronic idiopathic thrombocytopenic purpura (ITP) a transient remission of thrombocytopenia was observed after intercurrent measles infection. Both cases were girls who had a long history of thrombocytopenia. During acute measles infection, the delayed hypersensitivity response was suppressed. Total T lymphocytes, T-cell subsets, especially OKT4 cells, the lymphoproliferative response, and interleukin-2 (IL-2) and gamma-interferon production were decreased accompanying normalization of the OKT4/OKT8 ratio. However, OKT4 cells remained at a reasonably low level and the lymphoproliferative response stimulated with pokeweed mitogen was still in the lower normal range. Direct immunofluorescent study demonstrated that the measles antigen was present in the mononuclear cells, especially OKT4 cells. The levels of platelet-associated IgG antibody (PAIgG) and IgG circulating immune complex (CIC) were undetectable. One month later, the OKT4/OKT8 ratio lymphoproliferative response significantly increased, IL-2 and gamma-interferon production increased, and PAIgG and IgG CIC reappeared with the relapse of thrombocytopenia. There was also a significant increase in in vitro IgG production due to the presence of patient OKT8 cells and/or OKT4 cells. However, there was no enhancement in the presence of patient B cells. This suggests that the presence of specific OKT4 helper T cells and a defect in the suppressor function of suppressor OKT8 cells contribute to an overproduction of IgG and the appearance of PAIgG accompanied by thrombocytopenia. The transient remission associated with measles infection is probably related to the effect of the virus on the helper T cells, resulting in a decrease in specific OKT4 helper T cells and normalization of the OKT4/OKT8 ratio, suppression of IL-2 and gamma-interferon production, and platelet-associated IgG production.