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n. The reaction of a lymphocyte or antibody with an alloantigen.

"Debré, Judith Kapp, and Carl Waltenbaugh; we analyzed the specificity of cytolytic T lymphocyte in relation to Ir gene function with Steven Burakoff and Robert Finberg and demonstrated how alloreactivity arises as a consequence of the commitment of T lymphocytes to recognize antigen in the context of autologous MHC gene products."