Thrombocytopenia, low platelet volume, high IgA and IgE with normal IgG and/or decreased IgM, low isohemagglutinin levels, lymphopenia with low CD8+ T cells, increased proportion of effector memory T lymphocytes, normal T-cell proliferation upon PHA but reduced T-cell proliferation upon anti-CD3 stimulation, autoimmune cytopenias. This evidence concerns the gene CD8A and lymphopenia.