Retinol and retinal metabolism. Relationship to the state of differentiation of cultured human keratinocytes.

The modes of action of the five major endo-(1----4)-beta-D-glucanases (I, II, III, IV and V) purified from Penicillium pinophilum cellulase were compared by h.p.l.c. analysis, with normal, 1-3H-labelled and reduced cello-oligosaccharides and 4-methylumbelliferyl glycosides as substrates. Significant differences were observed in the preferred site of cleavage even when substrates with the same number of glycosidic bonds were compared. Thus, although endoglucanase I was unable to attack normal cello-oligosaccharides shorter than degree of polymerization 6, it hydrolysed reduced cellopentaose to yield cellotriose and cellobi-itol, and it produced cellotriose and 4-methylumbelliferyl glucoside from 4-methylumbelliferyl cellotetraoside. Endoglucanase IV hydrolysed [1-3H]cellotriose but did not attack either cellotri-itol or 4-methylumbelliferyl cellobioside. These and other anomalous results indicated clearly that modification of the reducing glycosyl residue on the cello-oligosaccharides induces in an apparent change in the mode of action of the endoglucanases. It is suggested that, although cello-oligosaccharide derivatives are useful for differentiating and classifying endoglucanases, conclusions on the mechanism of cellulase action resulting from these measurements should be treated cautiously. Unequivocal information on the mode of endoglucanase action on cello-oligosaccharides was obtained with radiolabelled cello-oligosaccharides of degree of polymerization 3 to 5. Indications that transglycosylation was a property of the endoglucanases were particularly evident with the 4-methylumbelliferyl cello-oligosaccharides. Turnover numbers for hydrolysis of the umbelliferyl cello-oligosaccharides were calculated, and these, along with the other analytical data collected on the products of hydrolysis of the normal, reduced and radiolabelled cello-oligosaccharides, suggested that the various endoglucanases had different roles to play in the overall hydrolysis of cellulose to sugars small enough to be transported through the cell membrane.     

Biologically active interleukin 1 in human eccrine sweat: site-dependent variations in alpha/beta ratios and stress-induced increased excretion

Human eccrine sweat devoid of epidermal protein contamination was collected from palms, soles, and different sites on the trunk. Interleukin 1 alpha (IL 1 alpha) and interleukin 1 beta (IL 1 beta) content were analyzed for immunoreactivity by enzymo-immunoassay and immunoblotting and for bioactivity by the stimulation of prostaglandin E2 (PGE2) production in human dermal fibroblasts. The bioassay was validated by using blocking antibodies against IL 1 alpha and beta. All sweat samples were found to contain significant amounts of immunoreactive and biologically active IL 1. The immunoreactive forms were at 17 kDa as shown by immunoblotting analysis, indicating that they were mature (secreted), undegraded IL 1 peptides. Whereas IL 1 alpha was detectable in sweat samples obtained from both truncal and palmo-plantar regions, IL 1 beta was only detectable in the sweat of palms and soles (IL 1 alpha/beta ratio greater than 700 in trunk and 5.4 in palms and soles) indicating a site-dependent difference in the excretion of the two IL 1 molecules. IL 1 concentration was high in spontaneous (IL 1 alpha, 3.7; IL 1 beta, 0.3 ng/mL) and pilocarpine induced sweat (IL 1 alpha, 3.9; IL 1 beta, 1.2 ng/mL), and it was much increased during jogging and sauna (IL 1 alpha, 22.6; IL 1 beta, 3.3 ng/mL). This does not appear to represent an excretory process aimed at clearing blood IL 1, but rather a stress-induced increased production of IL 1 by sweat gland cells.     

Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence

Natural selection, in the form of balancing selection or selective sweeps, can result in a decoupling of the amounts of molecular polymorphism and divergence. Thus natural selection can cause some areas of DNA sequence to have greater silent polymorphism, relative to divergence between species, than other areas. It would be useful to have a statistical test for heterogeneity in the polymorphism to divergence ratio across a region of DNA sequence, one that could identify heterogeneity greater than that expected from the neutral processes of mutation, drift, and recombination. The only currently available test requires that a region be arbitrarily divided into sections that are compared with each other, and the subjectivity of this division could be problematic. Here a test is proposed in which runs of polymorphic and fixed sites are counted, where a "run" is a set of one or more sites of one type preceded and followed by the other type. The number of runs is smaller than otherwise expected if polymorphisms are clumped together. By simulating neutral evolution and comparing the observed number of runs to the simulations, a statistical test is possible which does not require any a priori decisions about subdivision.      

Lectin-mediated induction of IL-4-producing CD4+ T cells.

Cultured murine CD4+ T cells have been shown to differentiate into IL-2 or IL-4-producing subsets. The factors responsible for the development of CD4+ T cells which produce IL-2 but not IL-4 and cells capable of producing IL-4 but not IL-2 are unknown. Here we describe a system that allows the controlled induction of IL-2- or IL-4-producing T cells after one single round of activation. Freshly isolated CD8-depleted T cells were activated with various polyclonal T cell activators for 48 h, washed, and then expanded under different conditions. IL-2 and IL-4 production were induced by restimulation of T cells and were measured with CTLL cells that respond to both cytokines and mAb to IL-2 and IL-4. T cells produced mainly IL-2 and small amounts of IL-4 when restimulated after expansion culture for 12 days with rIL-2 alone. However, after expansion for 12 days in the presence of rIL-2 plus Con A, we observed a 30- to 100-fold up-regulation of IL-4 activity and a 100-fold down-regulation of IL-2 when assessed by responses of CTLL cells incubated with the supernatant of restimulated T cells and by responses of CTLL cells cocultured with restimulated cells. An increase of IL-4 and decrease of IL-2 was also observed when the results were based on the cell numbers at the beginning of the expansion culture. The induction of IL-4 and the down-regulation of IL-2 1) were not reproduced with alpha-methyl-mannoside-treated supernatant of Con A-stimulated spleen cells, 2) were not dependent on the presence of large numbers of APC, 3) did not result from differential consumption of lymphokines after restimulation, 4) were not due to a difference in the time course of IL-2 or IL-4 release in either T cell population, and 5) were obtained regardless of the agents used to activate or to restimulate the T cells. Because Con A remained detectable on the T cell surface and because expansion of activated T cells with IL-2 plus Con A for several days was necessary, our results indicate that mainly IL-4-producing CD4+ T cells can be induced by prolonged engagement of T cell surface molecules.     

Interleukin 1 receptor antagonist in human epidermis and cultured keratinocytes.

Interleukin 1 (IL-1), present in high amounts in normal human skin without any sign of inflammation, suggests a complex mechanism by which its bioactivity is regulated. The specific receptor antagonist of IL-1 (IL-1ra) was analyzed in human skin, sweat and cultured keratinocytes. Extracts of both skin and cultured keratinocytes blocked the binding of [125I]IL-1 to its receptor whereas sweat did not. The inhibitory activity was cell-associated, was not secreted by cultured keratinocytes, and IL-1ra mRNA was identified in these cells. There was an inverse relationship between the level of IL-1ra and that of IL-1 alpha and beta since extracts of differentiating keratinocytes (DK) and higher IL-1ra levels and expressed more mRNA for IL-1ra than non-differentiated keratinocytes (NDK), whereas NDK contained 4 times more IL-1 alpha and beta proteins than DK. This association of cell differentiation with a shift in agonist/antagonist ratio might be related to important autocrine or paracrine functions of IL-1 in normal and inflamed human skin.     

Central role for TCR/CD3 ligation in the differentiation of CD4+ T cells toward A Th1 or Th2 functional phenotype.

Activated CD4+ T cells can be classified into distinct subsets; the most divergent among them may be considered to be the IL-2 and IFN-gamma-producing Th1 clones and the IL-4 and IL-5-producing Th2 clones. Because Th1 and Th2 clones can usually be detected only after several months of culture, we used conditions that modulate the IL-2 and IL-4 production in short term culture. Here we show that freshly isolated and subsequently in vitro-activated CD4+ T cells that were cultured for 11 days with rIL-2 and restimulated showed a IFN-gamma+ IL-2+ IL-3+ IL-4- IL-5- pattern. Because these cells were not capable of providing B cell help for IgG1, IgG2a, or IgE in an APC- and TCR-dependent T-B cell assay, they expressed a phenotype typical for most Th1 clones. In contrast, activated T cells that were cultured for 11 days with IL-2 plus a mAb to CD3 and then restimulated produced a IFN-gamma- IL-2- IL-3+ IL-4+ IL-5+ pattern. These cells were capable of providing B cell help for IgG1, IgG2a, and IgE synthesis and thus presented a phenotype typical for Th2 clones. Similar results were observed when mitogenic mAb to Thy-1.2 or to framework determinants of the alpha beta TCR were used. The induction of Th1- and Th2-like cells did not depend on the relative expression of CD44 or CD45 by the T cells before activation in vitro. Because the incubation of activated T cells with anti-CD3/TCR mAb induced high unrestricted lymphokine production, the latter might be responsible for the Th2-like lymphokine pattern observed after restimulation. To address this point, TCR V beta 8+ and V beta 8- T cell blasts were co-cultured in the presence of mAb to V beta 8. After restimulation, V beta 8+ cells had a IL-4high IL-2low phenotype and V beta 8- cells had a IL-4low IL-2high phenotype. This demonstrates that TCR ligation but not lymphokines alone are capable of inducing Th2-like cells, and this points out a central role for the TCR in the generation of T cell subsets.