Immunoarchitecture of the bone marrow in neutropenia: Increased HNK‐1 + cells define a subset of neutropenic patients

An immunoperoxidase technique was used to examine the distribution of lymphocyte subsets in bone marrow biopsies of 15 patients with neutropenia and seven non‐neutropenic controls. The bone marrow of most patients and controls had similar distributions of immune effector cells characterized by a diffuse array of predominantly cytotoxic/suppressor T‐cells and occasional nodular aggregates of helper T‐cells. Cells displaying the natural killer cell marker HNK‐1 were sparse in controls and most neutropenic patients. However, marked increases in marrow HNK‐1 + cells were identified in four of the 15 patients. Three of these patients had diffuse HNK‐1 + infiltrates associated with increased Leu 4+ (OKT‐3 +) T‐cells while one had a nodular HNK‐1 + infiltrate associated with small B‐cell follicles. Each of these patients had clinical features similar to those described in the large granular lymphocyte (LGL) lymphocytosis (leukemia) syndrome, but only one of four demonstrated persistently increased numbers of LGLs in the peripheral blood. Thus, this study extends the association of neutropenia and increased numbers of cells with a T/NK phenotype to include patients whose bone marrow is the only demonstrable site of involvement. Since morphologic examination of the bone marrow could not identify the bone marrows with increased HNK‐1 + cells, immunulogic techniques are required to detect these cases.