Abstract
The distribution of natural killer cells in human spleen was studied immunohistochemically and immuno-electron microscopically using a monoclonal antibody for human natural killer cell (HNK-1). The reactivity of this antibody to the formalin fixed and paraffin embedded specimens was confirmed and technical improvement was attempted. HNK-1+ cells were divided into two groups according to their distribution and cytological characteristics. One group consisted of cells distributed around the white pulp and in the red pulp and the other group localized in the germinal center (GC). The former morphologically resembled large granular lymphocyte (LGL) of peripheral blood and was thought to be the LGL of the blood circulating in the spleen. Although the latter consisted of lymphocytes having electron dense granules as LGL, their size and the ratio of nucleus to cytoplasm were greater than those of the former and their ultrastructural appearance indicated promoted secretory activity. The number of HNK-1+ cells in GC was intimately related to the development of GC. Furthermore, their population correlated with the number of mitoses of centroblasts, tingible body macrophages or peanut lectin-bound immature B lymphocytes, respectively. Based on these facts, a possibility was suggested that HNK-1+ cells in GC might be in an active phase and they might be related to the physiological regulation of differentiation and expansion of B cell. Phenotypic expression of HNK-1+ cells was examined by double immunoenzymatic labelling, but no differences were found between the HNK-1+ cells in GC and in the red pulp.
