RESUMO
CD1a, an antigen-presenting molecule related to major histocompatibility complex (MHC) class I, is frequently described as nonpolymorphic. In humans it is dimorphic, due to two linked amino acid substitutions in the alpha1 domain (Ile13Thr and Trp51Cys). The CD1a gene on chromosome 1 is not linked to MHC and may be mismatched between human leukocyte antigen-identical siblings. We analyzed 155 donor-recipient pairs of the Eurobank cohort, 141 matched for CD1a and 14 unmatched in the graft-versus-host disease (GVHD) direction. The burden of GVHD was not increased by CD1a mismatching. The incidence of GVHD in matched and unmatched groups was respectively: grade I-IV: 81% and 86% (P = 0.492); II-IV 61% and 57% (P = 0.495); III-IV 23% and 21% (P = 0.608). Adjusting for age, sex mismatch, GVHD prophylaxis, and conditioning did not reveal any significant difference. This suggests that, unlike conventional class I molecules, CD1a does not function as a transplantation antigen and does not require matching in hematopoietic stem cell transplantation.