Human CD100, a novel leukocyte semaphorin that promotes B-cell aggregation and differentiation.

Herein we describe the molecular characterization of the human leukocyte activation antigen CD100 and identify it as the first semaphorin, to our knowledge, in the immune system. Semaphorins have recently been described as neuronal chemorepellants that direct pioneering neurons during nervous system development. In this study we demonstrate that CD100 induces B cells to aggregate and improves their viability in vitro. We show that CD100 modifies CD40-CD40L B-cell signaling by augmenting B-cell aggregation and survival and down-regulating CD23 expression. Thus, these results suggest that semaphorins as exemplified by CD100 also play a functional role in the immune system.     

Case report 329

Skeletal Radiology -     

CD5, CD10, and CD23 expression in Waldenstrom's macroglobulinemia

CD5, CD10, and CD23 are cell surface antigens used to distinguish B-cell disorders. The expression of these antigens and their clinical significance in Waldenstrom's macroglobulinemia (WM), an uncommon B-cell disorder, remains to be clarified. We therefore determined expression of CD5, CD10, and CD23 by flow cytometric analysis on bone marrow lymphoplasmacytic cells (CD19+ k/l light chain restricted) for 171 serially biopsied patients with findings of the consensus panel definition of WM. Importantly, we also correlated laboratory and clinical data, as well as existence of a familial history of a B-cell disorder in view of reports suggesting familial predisposition in WM. These studies demonstrated tumor cell expression of CD5, CD10, and CD23 in 15 of 171 patients (9%), 11 of 161 patients (7%), and 37 of 105 patients (35%), respectively. Coexpression of CD23 with CD5 or CD10 was common. Tumor Lymphoplasmacytic from 10 of 15 (66%) and 3 of 11 (27%) patients with WM that expressed CD5 and CD10, respectively, also showed expression of CD23 (P = 0.01 and P = 0.08, respectively). Among patients with CD23 expression, increased serum immunoglobulin (Ig) M levels were observed compared with patients without CD23 expression (P = 0.05). No differences in age at diagnosis; presence of adenopathy and/or splenomegaly; bone marrow involvement; serum IgA, IgB, and b2 macroglobulin levels; hematocrit; platelet count; or familial history of WM or a related B-cell disorder were observed among patients with and without CD5, CD10, and CD23 expression. These studies demonstrate that CD5, CD10, and CD23 are commonly found in WM and that their expression should not exclude the diagnosis of WM. Moreover, expression of CD23 may define a clinically distinct subset of patients with WM.     

The ultrastructural localization of secretory acid phosphatase in giant cell tumor of bone.

Three cases of giant cell tumor of bone were studied with the light and electron microscopes to determine the histochemical and cytochemical distribution of acid phosphatase isoenzymes. Using beta-glycerophosphate as a nonspecific substrate, acid phosphatase was found in the giant cells as well as the stromal cells. Ultrastructurally, using this substrate, the enzyme was found to be associated with lysosomes in the stromal cells and giant cells and also with the profuse system of tubules and vesicles in the cytoplasm of the giant cells. Using phosphorylcholine and D-ephedrinephosphate, which are substrates for a specific secretory isoenzyme of acid phosphatase, activity was found only in the vesicles of the giant cell cytoplasm. Lysosomes did not show activity with these substrates. Multinucleated cells of giant cell tumor contain a specific secretory type of acid phosphatase which is not present in the stromal cells. This suggests that the giant cells are attempting to form a secretory system similar to osteoclasts and that the vesicles in the cytoplasm which contain this acid phosphates are the morphologic expression of an abortive secretory system.     

Stimulation of Synthesis of Free Chondroitin Sulfate Chains by β-D-Xylosides in Cultured Cells

Previous studies have shown that D-xylose partially overcomes the puromycin inhibition of chondroitin sulfate synthesis in cultured chick embryo chondrocytes. Likewise, D-xylose stimulates chondroitin sulfate synthesis by limb bud mesenchyme cells previously treated with BrdU or limb bud cartilage cells treated with puromycin. The studies reported here show that p-nitrophenyl-beta-D-xylopyranoside and 4-methyl-umbelliferyl-beta-D-xylopyranoside cause a much greater stimulation than does D-xylose and are active at much lower concentrations. In contrast to D-xylose, the xylosides strikingly stimulate chondroitin sulfate synthesis in predifferentiated mesenchyme cells. The xylosides stimulate synthesis of chondroitin sulfate by rat glial cell tumor cells (RC-6), a mouse neuroblastoma (C1300, NB41A), and two strains of cultured rat hepatoma cells (HTC, H(4)). These results indicate that certain types of nonconnective tissue cells contain the enzymic machinery for synthesis of chondroitin sulfate which is normally not utilized because of limited synthesis of core protein and/or xylosyltransferase. The beta-xylosides may be used as a probe of the capacity of various cell types to synthesize sulfated glycosaminoglycans.