In the human spleen the marginal zone (MZ) contains medium-sized B cells with a distinct immunophenotype. A main function attributed to the MZ is its involvement in the primary response to blood-borne antigens, in particular to thymus-independent antigens type 2. In this study the presence of antigens related to activation and proliferation was evaluated in human spleens by immunohistochemical staining. It appeared that MZ B cells do not show interleukin 2 receptor expression, and are in G0 phase of the cell cycle, as demonstrated by the lack of Ki-67 reactivity. The most interesting finding is the high CD21 expression by MZ B cells in the absence of IgD expression. As the CD21 antigen has been shown to be involved in B cell activation in close linkage with IgM, it can be suggested that MZ B cells are particularly well equipped for rapid and easy activation in a primary immune response.

In most cases of small-cell lung carcinomas (SCLC) phenotypic features compatible with a neuroendocrine differentiation status can be identified by monoclonal (MOC) antibody-based immunohistological procedures. Similar features can be recognized only in a minority of non-SCLC tumors. During a period of 30 months, all diagnostic non-SCLC biopsies (141 cases) were prospectively analysed for the presence of markers indicative for neuroendocrine differentiation. In 31% of all cases, such a presence could be noticed. Neuroendocrine differentiation (50% to 100% positive-staining tumor cells) was recognized more frequently in adenocarcinoma when compared to large-cell and squamous-cell carcinoma (chi 2 = 9.31, 2 degrees of freedom, P less than 0.01). To investigate whether the clinical behavior of these "neuroendocrine" non-SCLC cases mimics SCLC, a multivariate analysis for prognostic factors was performed. Among other prognostic factors, biopsies containing more than 50% positive-staining tumor cells with the MOC antibody-1 (MOC-1) were recognized as negative prognostic factors.

Mesangial cell (MC) proliferation and extracellular matrix (ECM) formation are hallmarks of chronic glomerular disease. The present in vitro study examined the effects of the vasoactive agents angiotensin II (Ang II), arginine vasopressin (AVP), and serotonin (5-HT) on growth and protein biosynthesis of cultured rat MCs after 72 hours of incubation. AVP and 5-HT (10(-6) M) significantly increased DNA synthesis and growth of quiescent subconfluent MCs to levels of 25 and 45%, respectively, of the optimal stimulatory effect of 10% fetal calf serum (FCS) (both P less than 0.001). The mitogenic effect of Ang II was 10% of the 10% FCS effect (P less than 0.01). ECM production was studied by ELISA assay for fibronectin (FN) secreted into the culture medium (SeFN) and cell-associated FN, that is, intra- and pericellular FN (CaFN). In all incubations, highly significant negative linear relationships were found between the numbers of MCs per well and quantities of both SeFN and CaFN after normalization of the data by logarithmic transformation (SeFN: r values greater than -0.9705; CaFN: r greater than -0.9620; P less than 0.001). Thus, increasing cell densities progressively suppressed ECM formation by MCs. The ECM production was found to be independent of growth activity. AVP significantly increased SeFN (P less than 0.05) and decreased CaFN (P less than 0.001) in subconfluent cultures; Ang II and 5-HT had no effect. Metabolic labeling with 35S-methionine (18 hr, 200 microCi/ml medium) and 2-D electrophoresis of MC lysates resulted in resolution of greater than 500 different radiolabeled intracellular proteins in molecular weight from 110 to 20 Kd over an isoelectric interval of 5.0 to 7.0.(ABSTRACT TRUNCATED AT 250 WORDS)

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A single injection of D-galactosamine hydrochloride induces acute self-limiting liver disease in rats that morphologically resembles drug-induced hepatitis in human beings. In this immunohistochemical study we examined the localization and expression of the hepatic extracellular matrix components fibronectin, laminin, collagen type I, collagen type III and collagen type IV and of the cell surface receptors (integrins) for fibronectin and laminin. Sections of liver tissue obtained at intervals of 6, 12, 18, 24, 30, 36, 48 and 72 hr and 7 and 21 days after galactosamine administration were immunostained with a panel of polyclonal monospecific antibodies and studied independently by two of us. Fibronectin was the first extracellular matrix component found to be increased, 12 hr after galactosamine injection, followed by collagen type III, and, in a later phase, collagen type IV, type I and laminin. Increased deposition of extracellular matrix was found in areas with liver cell necrosis and along sinusoids. Extracellular matrix immunoreactivity reached a maximum at 36 to 48 hr and decreased thereafter to preinjury levels 3 wk after galactosamine. Immunostaining for the fibronectin and laminin receptors revealed tissue localization identical to that of their ligands. However, the intensity of staining was opposite of that for the extracellular matrix, with a decrease of immunoreactivity after 24 to 48 hr. The observed sequence of changes in hepatic extracellular matrix proteins after galactosamine injection resembles the repair reaction in other tissues and may reflect the particular function that each carries out during the process of liver healing after toxic injury.