Receptors for immunoglobulin isotypes (FcR) on murine T cells: II. Multiple FcR induction on hybridoma T cell clones

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Abstract
In the preceding report (Eur. J. Immunol.1985. 75: 662), we described a variety of receptors for the Fc portion of the different isotypes of mouse immunoglobulins (FcR), that were found to be expressed on hybridoma T cell clones. In the present work, we wondered whether the expression of these T cell FcR would be regulated by environmental influences such as the presence of corresponding ligands. We found that exposing the cells to the bulk of serum immunoglobulins in vivo, or to purified monoclonal immunoglobulins in vitroboth resulted in FcR induction. The expression of all constitutive receptors, i.e.Fcγ1/2bR, Fcγ3R, FcαR and FcϵR, could be increased upon incubation with IgG1, IgG2b, IgG3, IgA and IgE, respectively. After induction, the specificity of FcR was not modified. Two FcR were detectable only upon induction. These were Fcγ2a/2b/1R, induced by IgG2a and FcμR, induced by IgM. Interestingly, FcR detectable after induction only were short‐lived at the membrane. Ten to 15 h after induction they were not detected any more, whereas the expression of constitutive FcR remained elevated for at least 24 h following induction.Therefore, depending on the concentration of immunoglobulins in the environment, and depending on whether they are short lived or long lived, FcR can modulate their expression on the membrane of T cells. Such a versatility might be an efficient means to contribute to isotypic regulation through the release of regulatory immunoglobulin‐ binding factors.