Enzyme histochemical observations on the localization and structure of the T cell and B cell regions in the human spleen

Summary

The capacity of certain B-lymphocytes to bind complement (demonstrated by erythrocyte-antibody-complement complexes, EAC) was used as a marker of the B-lymphocyte regions of the human white splenic pulp. This was carried out on cryostat sections in order to correlate enzyme histochemical findings (5-nucleotidase, ATPase, acid phosphatase, nonspecific esterase, alkaline phosphatase) to immunological functions. EAC were typically found in the follicle centers and marginal zone, whereas periarteriolar lymphocyte sheaths remained negative. The enzyme histochemical patterns of lymphocytes and reticulum cells allowed a clear distinction between areas with and those without EAC-binding. This was shown most clearly when the following enzymes were demonstrated in combination: 5-nucleotidase (5-Nase) + alkaline phosphatase, ATPase + acid phosphatase, and nonspecific esterase + acid phosphatase. 5-Nase correlated best to EAC-positive areas with a positive reaction in follicle wall lymphocytes and dendritic reticulum cells, whereas periarteriolar sheaths contained no 5-Nase-positive structures. Reticulum cells around periarteriolar lymphocyte sheaths at the margin of the red splenic pulp showed a particularly strong alkaline phosphatase reaction. The reticulum cells of the areas containing B-lymphocytes and those of the EAC-negative periarteriolar regions, which probably contain T-lymphocytes, were specifically labeled for different sets of enzymes. These findings suggest that specialized, morphologically different reticulum cells may be the “guide rails” for the different freely circulating lymphocyte populations.