B-cell lymphopoiesis is regulated by cathepsin L.

Cathepsin L (CTSL) is a ubiquitously expressed lysosomal cysteine peptidase with diverse and highly specific functions. The involvement of CTSL in thymic CD4+ T-cell positive selection has been well documented. Using CTSL(nkt/nkt) mice that lack CTSL activity, we have previously demonstrated that the absence of CTSL activity affects the homeostasis of the T-cell pool by decreasing CD4+ cell thymic production and increasing CD8+ thymocyte production. Herein we investigated the influence of CTSL activity on the homeostasis of peripheral B-cell populations and bone marrow (BM) B-cell maturation. B-cell numbers were increased in lymph nodes (LN), spleen and blood from CTSL (nkt/nkt) mice. Increases in splenic B-cell numbers were restricted to transitional T1 and T2 cells and to the marginal zone (MZ) cell subpopulation. No alterations in the proliferative or apoptosis levels were detected in peripheral B-cell populations from CTSL (nkt/nkt) mice. In the BM, the percentage and the absolute number of pre-pro-B, pro-B, pre-B, immature and mature B cells were not altered. However, in vitro and in vivo experiments showed that BM B-cell production was markedly increased in CTSL (nkt/nkt) mice. Besides, BM B-cell emigration to the spleen was increased in CTSL (nkt/nkt) mice. Colony-forming unit pre-B (CFU pre-B) assays in the presence of BM stromal cells (SC) and reciprocal BM chimeras revealed that both BM B-cell precursors and SC would contribute to sustain the increased B-cell hematopoiesis in CTSL (nkt/nkt) mice. Overall, our data clearly demonstrate that CTSL negatively regulates BM B-cell production and output therefore influencing the homeostasis of peripheral B cells.

Anticuerpos monoclonales: diagnóstico por inmunohistoquímica / Monoclonal antibodies: immunohistochemical diagnosis

Immunohistochemistry allows pathologists to examine the presence of specific cell products in tissue sections. It provides a bridge between the morphological and functional aspects of a lesion since it allows for the examination of the presence and/or abscence of a product "in situ". The use of monoclonal antibodies offer advantages over policlonal antisera. Bacground staining is usually low vecause of the high specificity of monoclonal antibodies and the absence of "unwanted antibodies" present in policlcocnal antisera. Standardization of protocols is possible due to the reliable affinity and titre of monoclonal antisera. However there are some disadvantages with the use of monoclonal antibodies. Paradoxically they are related to the hight specificity of these antibodies. The single antigenic determinant recognized by a monoclonal antibody can and is often denatured or destroy by fixation. Also this single antigenic determinant may be present in different substances and are capable of an specifric but undesirable staining. There are some technical tricks to aboid both problems. In the future most substance will be reconized by monoclonal antibodies and so the histophatologic diagnosis will achieved an objective nature