Activation of ferret erythrocyte Na+–K+–2Cl− cotransport by deoxygenation

Deoxygenation of ferret erythrocytes stimulates Na⁺–K⁺–2Cl⁻ cotransport by 111% ( s.d. , 46) compared to controls in air. Half-maximal activation occurs at a P _O2 of 24 mmHg ( s.d. , 2) indicating that physiological changes in oxygen tension can influence cotransport function. Approximately 25–35% of this stimulation can be attributed to the rise of intracellular free magnesium concentration that occurs on deoxygenation (from 0.82 ( s.d. , 0.07) to 1.40 m m ( s.d. , 0.17)). Most of the stimulation is probably caused by activation of a kinase which can be prevented or reversed by treating cells with the kinase inhibitors PP1 or staurosporine, or by reducing cell magnesium content to submicromolar levels. Stimulation by deoxygenation is comparable with that caused by calyculin A or sodium arsenite, compounds that cause a 2- to 3-fold increase in threonine phosphorylation of the cotransporter which can be detected with phospho-specific antibodies. However, the same approach failed to detect significant changes in threonine phosphorylation following deoxygenation. The results suggest that deoxygenation causes activation of a kinase that either phosphorylates the transporter, but probably not on threonine, or phosphorylates another protein that in turn influences cotransporter behaviour. They also indicate that more than one kinase and phosphatase are involved in cotransporter phosphorylation.     

CD8+ T Cells Induce Medullary Thymic Epithelium and CD4+CD8+CD25+ TCRβ− Thymocytes in SCID Mice

During T-cell development the transition in the thymus of CD4-CD8- double negative (DN) progenitor T cells into CD4+CD8+ double positive (DP) cells is dependent on the expression of a T-cell receptor (TCR)-beta-chain protein. In this study purified peripheral CD4+ and CD8+ T lymphocytes from the C.B-17 strain of mice were adoptively transferred into syngeneic, neonatal SCID mice, where donor cells resided at constant numbers in thymus from 2 weeks until 10 weeks post cell transfer. In the recipient thymus the CD8+ donor cells outnumbered the CD4+ cells by a factor of three to five and both subsets contained a large fraction of activated cells. During the late phase of treatment, CD8+ T cells induced high numbers of DP thymocytes in the SCID mice, a process accompanied by the maturation of medullary epithelial cells. Such thymic development in the SCID mouse was inhibited by coresiding CD4+ donor T cells. These results indicate a regulatory role by mature peripheral T cells on medullary epithelial growth and thymocyte development in the treated SCID mice.     

Increased occurrence of IgE+ and FcεRI+ cells in adenoids from atopic children

BACKGROUND: To examine the influence of atopy on the different cell populations in adenoids, we investigated the presence of IgE+ cells, cells expressing the high-affinity receptor for IgE (Fc(epsilon)RI), and various other cell populations in adenoid tissue, in atopic and nonatopic children with otitis media with effusion (OME) or adenoid hyperplasia (AH). METHODS: Cryostat sections of adenoids from 14 atopic and 16 nonatopic children suffering from long-lasting OME (n=15) or obstructive AH (n=15) were investigated with immunohistochemical markers for T-cell subsets, mast cells, eosinophils, plasma cells, CD25, CD1a, IgE, and Fc(epsilon)RI. RESULTS: Sensitization to allergens was correlated to an increase of IgE+ cells in the epithelium (P<0.01), the extrafollicular area (P<0.0001), and the follicles (P<0.001) of the adenoids and an increase of Fc(epsilon)RI+ cells in the extrafollicular area (P<0.01). A minority of the IgE+ cells were plasma cells. No significant differences in cells stained for IgE, Fc(epsilon)RI, or the other markers were observed between patients with OME and AH. CONCLUSIONS: Atopy is associated with increased numbers of IgE+ and Fc(epsilon)RI+ cells in adenoids irrespective of whether the child has OME or AH.