The periarteriolar lymphocyte sheath in immunodeficiency T- or B-lymphocyte area?

T- and B-lymphocyte populations in peripheral lymphoid tissues occur in distinct compartments (e.g., the periarteriolar lymphocyte sheath of the splenic white pulp is a T-cell area). The authors report on two patients with severe combined immunodeficiency (SCID) and one patient with immunodeficiency after anti-T-cell treatment for rejection of a heart transplant, in which the area surrounding the central arteriole in spleen white pulp was well-populated despite T-cell deficiency (documented by, for example, severe depletion of lymph node paracortex). Immunologic phenotyping showed the B-lymphoid lineage of lymphocytes at this location. The framework in the periarteriolar area consisted of follicular dendritic cells, which are typical framework components of B-cell areas. We conclude that assessment of only conventional histopathology of the spleen in these patients leads to erroneous conclusions about the type of immunodeficiency and that immunologic phenotyping is required to document the exact nature of the deficiency.