Immunohistochemical and HLA typing studies of a premature baby (female, 24 gestation weeks, 651g at birth) with post-transfusion graft-versus-host disease were presented. After clinical manifestation of the disease, HLA typing of the patient blood showed positivity for HLA-A24 which was theoretically absent from HLA typing of her parents. It was suggested that HLA-A24 positive lymphocytes must have been derived from one of the blood donors. In order to confirm these results, immunohistochemical study was performed on biopsied skin by using anti-HLA-A24 monoclonal antibody, HU-49. Lymphocytes infiltrating in the skin, mainly at the epidermo-dermal juncton showed strong positivity for HU-49 reactive antigen. In addition, the majority of those lymphocytes was Leu-2a positive. The collective evidence strongly indicates that the HLA-A24 and Leu-2a positive T cells derived from blood transfusion caused GVHD in this case. Lastly immunohistochemical analysis of the skin biopsy material using monoclonal anti-HLA antibodies appears to be useful for the early diagnosis of post-transfusion GVHD.
