ULTRASTRUCTURAL CHARACTERISTICS OF FC-EPSILON-R-POSITIVE BASOPHILS INTHE SPLEEN AND BONE-MARROW OF MICE IMMUNIZED WITH GOAT ANTI-MOUSE IGDANTIBODY

BACKGROUND: Previous work showed that injection of mice with goat anti -mouse IgD antibodies results in increased numbers of Fc(epsilon)R-pos itive, non-B, non-T cells in the spleen and Fc(epsilon)R-positive cell s in the bone marrow, and that some of these cells had ultrastructural features of basophils. Fc(epsilon)R-positive, non-B, non-T cells expr ess virtually all of the capacity of mouse splenic ''non-B, non-T cell s'' to produce interleukin-4 in response to stimulation by cross-linki ng of Fc(epsilon)R or Fc(gamma)R, or by the calcium ionophore, ionomyc in. EXPERIMENTAL DESIGN: The present study is a detailed ultrastructur al analysis of Fc(epsilon)R-positive bone marrow cells or Fc(epsilon)R -positive splenic non-B, non-T cells sorted from mice injected with go at anti-mouse IgD antibody and of Fc(epsilon)R-positive bone marrow ce lls or spleen cells pooled from normal mice not injected with goat ant i-IgD. RESULTS: Basophils represented the majority (90%) of the granul ated cells present in the Fc(epsilon)R-positive splenic non-B, non-T c ells or Fc(epsilon)R-positive bone marrow cells of goat anti-IgD-injec ted mice. In contrast, the cytoplasmic granule-containing Fc(epsilon)R -negative cells sorted from spleen or bone marrow of goat anti-IgD-inj ected animals contained predominantly a mixture of neutrophils, eosino phils, monocytes and their precursors. Both the Fc(epsilon)R-positive and -negative preparations contained rare (<5%) cells with ultrastruct ural features of very immature mast cells. Basophils were also identif ied in Fc(epsilon)R-positive cells sorted from total bone marrow cells or spleen cells of normal mice not injected with goat anti-IgD. CONCL USIONS: Taken together with data concerning the numbers of Fc(epsilon) R-positive, non-B, non-T cells in the spleen, and Fc(epsilon)R-positiv e B220-negative cells in the bone marrow, these ultrastructural findin gs indicate that injection of mice with goat anti-IgD results in incre ased numbers of basophils, particularly in the spleen, that exhibit an 8-fold increase in basophils as a result of injection of goat anti-Ig D.