Distribution of immunoglobulin-containing cells in human bone marrow and lymphoid tissues

Cell suspensions of human bone marrow, spleen, lymph nodes and palatine tonsils have been investigated for the presence of intracellular immunoglobulins by a direct immunofluorescence technique, using monospecific antisera against human Ig heavy chains alpha, mu and gamma and light chains kappa and lambda. Serum Ig levels were determined and the number of positive cells was compared with the concentration and calculated synthetic rate of serum Ig in each individual. The 28 patients studied covered a wide range of diagnoses and included those with normal as well as pathologically decreased or increased serum Ig levels. There was a high correlation between the calculated synthetic rate of each Ig class and the percentage of cells positive for the same Ig class in the bone marrow but not in the spleen, lymph nodes or tonsils. The Ig-containing cells constituted a much larger proportion of the total lymphoid cell population in the bone marrow than in the peripheral lymphoid organs. The estimated total number of Ig-containing cells was also much larger in the bone marrow than in the other organs investigated. It is concluded that in man the bone marrow is the major site of serum Ig synthesis and that the average synthetic rate per cell is the same regardless which of the three major Ig classes is produced. The role played by different lymphoid organs in humoral immunity is discussed in the light of the present results and reported data regarding lymphocyte and plasma cell kinetics in mammals.