A Light and Electron Microscopic Study of the Lymphomyeloid Complex in Hypervitaminosis A

Prolonged administration of vitamin Ato guinea pigs caused lymphomonocytosis and marked changes in organsof the lymphomyeloid complex, withproliferation of atypical mononuclearcells in the spleen, lymph nodes, andliver. In the bone marrow, atypicalmononuclear cell proliferation was alsoencountered and represented 13% ofthe entire marrow cell population insome animals. Electron microscopicexamination of the marrow revealedmany lymphocytes and plasma cellswith a well-developed rough endoplasmic reticulum (RER), suggesting thatthese cells are active in protein synthesis and antibody production. Theatypical mononuclear cells describedappeared to belong to the monocyticseries and contained a variety ofdense bodies, and a well-developedRER and Golgi apparatus. Vitamin Ais mitogenic, labilizes lysosomal andcell membranes, and can act as anadjuvant enhancing immune responses. It has been suggested thatvitamin A alters lymphoid cell membranes and enhances the degree ofimmune response by stimulation ofcell division in immunologically competent cells. The lesions describedhere may well be the morphologiccounterpart of an enhanced cellularimmune response.

Submitted on January 3, 1972 Revised on May 2, 1972 Accepted on May 5, 1972