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.

Compensatory renal growth protects mice against Shiga toxin 2-induced toxicity.

Uninephrectomy (Unx) is followed by the compensatory renal growth (CRG) of the remaining kidney. Previous evidence has shown that during CRG, renal tissue is resistant to a variety of pathologies. We tested the hypothesis that the functional changes that take place during CRG could attenuate Shiga toxin (Stx) toxicity in a mouse model of Stx2-induced hemolytic uremic syndrome (HUS). The participation of nitric oxide (NO) was analyzed. After CRG induction with Unx, mice were exposed to a lethal dose of Stx2, and the degree of renal damage and mortality was measured. Stx2 effects on the growth, renal blood flow (RBF) and NO synthase (NOS) intrarenal expression in the remaining kidney were then studied. The induction of CRG strongly prevented Stx2-mediated mortality and renal damage. Administration of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) during CRG partially impaired the protection. Both Stx2 and L-NAME interfered with the hypertrophic and hyperplastic responses to Unx, as well as with the increase in RBF. In intact mice, Stx2 decreased renal perfusion, inhibited endothelial NOS basal expression and enhanced inducible NOS expression; all of these effects were attenuated by prior Unx. It is concluded that during CRG mice are highly protected against Stx2 toxicity and lethality. The protective capacity of CRG could be related to the enhancement of renal perfusion and preservation of eNOS renal expression, counterbalancing two major pathogenic mechanisms of Stx2.

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

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 (AU)