FcγR expressed on T-cell hybrids: Specificity,behavior and relationship with Ia antigens |
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Authors: | Jean-Luc Teillaud Chantal Rabourdin-Combe Marc Stanislawski Catherine Neauport-Sautes Wolf Herman Fridman |
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Institution: | 1. Laboratoire d''Expérimentation Animale, Institut de Recherches sur les Maladies du Sang. Hôpital Saint-Louis, 75475 Paris Cedex 10, France;2. Laboratoire Immunologie Cellulaire France;3. Laboratoire de Chimie des Protéines, Institut de Recherches Scientifiques sur le Cancer, BP n° 8.94800 Villejuif, France |
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Abstract: | The fine specificity of receptor for the Fc portion of IgG (FcγR) expressed on T-cell hybrids secreting soluble FcγR (sFcγR) which suppresses antibody production, was investigated. FcγR was found to bind IgG from mouse, human, and rabbit species. It reacted with mouse IgG1 and IgG2a but not IgG2b, and human IgG1 and IgG3 but not IgG4. Mouse IgG and their subclasses bound more avidly to FcγR than human and rabbit IgG. FcγR of T-cell hybrids was sensitive to pronase and resistant to trypsin. In kinetics experiments, the behavior of FcγR on the membrane of T-cell hybrids was analyzed and compared to that of I-region-coded antigens expressed on these hybrids. Upon incubation at 37 °C in balanced salt solution (BSS), T-cell hybrids released FcγR into the medium. The reexpression of FcγR, after pronase cleavage or shedding, was complete within 3 hr of incubation in culture medium and required protein synthesis. I-A-coded antigens, present on these hybrids, disappeared simultaneously with FcγR upon incubation of cells at 37 °C in BSS. Within 3 hr of incubation in culture medium, although the reexpression of Fc°R was complete, no Ia antigens could be detected. They were reexpressed later, as tested after 19 hr of culture. During a single growth cycle, the expression of FcγR was maximal during log phase. |
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