An immune hypothesis of sexual orientation

Sexual orientation is encoded within immune-cell subsets (ICS) of mucosal a nd epithelial tissues. Gender orientation may be encoded within other ICS. Many immune cells: recognize and react to H-Y and H-X antigens; and enact t hese perceptions and reactions in accord with the perceiver's and the perce ived's MHC haplotype, XX or XY status, and immune-self recognition. Non-het erosexual orientations derive from excessive cross-priming, accompanied by clonal deletions, clonal expansions, anergy and tolerance. For at least som e tissues, cross-priming sufficient to induce altered orientations may occu r during critical periods of immunological development and can occur during fetal and infant development via maternal-fetal transfusion, placental pat hology, and impaired maternal nutrient-status or via excessive peripheral a poptosis during postnatal illness. Mast cell interactions with neurons illu strate how mucosal perceptions can be transduced into neuronal signals that modulate CNS events. This hypothesis is testable by mixed-lymphocyte react ions in appropriate cell subsets. Dendritic-cell immunizations are a potent ial therapy. (C) 2001 Harcourt Publishers Ltd.