COMPLEMENT RECEPTOR LYMPHOCYTES IN RABBIT .1. AN SIG-NEGATIVE SUBPOPULATION IN APPENDIX

  • 1 January 1976
    • journal article
    • research article
    • Vol. 117  (5) , 1805-1811
Abstract
Complement receptor lymphocytes (CRL) were detected in various rabbit lymphoid tissues by the ability of these CRL to form rosettes with sheep red blood cells coated sequentially with rabbit antiserum directed against sheep red blood cell stroma and horse serum as a nonhemolytic source of complement (EAC). The rosette assay was specific for complement receptor (CR) activity and the EAC detected C3b and C3d specific receptors. With lymphocyte preparations containing < 5% phagocytic cells, the average percent CRL in the various tissues studied was as follows: thymus 1%, popliteal lymph node 18%, spleen 30%, appendix 35% and peripheral blood 45%. Double assays in which the lymphocytes were prestained with an FITC[fluorescein isothiocyanate]-labeled Fab'' fragment of a goat anti-rabbit Fab antibody before rosetting indicated that CRL were a subpopulation of surface immunoglobulin (SIg)-bearing lymphocytes in popliteal lymph node, spleen and peripheral blood. In the appendix, in addition to finding SIg+ CR+ and SIg+ CR- populations, an SIg- CR+ population was consistently found. Double assays employing FITC-labeled goat antibodies specific for .mu., .alpha. and .gamma. determinants were also performed to determine if there was any relationship between the class of Ig displayed and presence of CR. It appeared that an approximately equivalent percentage of IgM- and IgG-bearing cells also displayed CR. Experiments in which appendix cells were treated with Pronase to remove SIg and CR and the cells cultured in vitro to allow regeneration of surface markers confirmed the existence of SIg+ CR+, SIg+ CR- and SIg- CR+ lymphocyte subpopulations. Whether the SIg- CR+ population represents a developing B [bone marrow-derived] cell population which eventually also expresses SIg or whether it belongs to the T [thymus-derived] or null cell populations is unclear at present.

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