Immunoglobulin-bearing cells in bone marrow of mice after prolonged treatment with anti-IgM antibodies

Abstract

IN the chicken, differentiation of immunoglobulin (Ig)-bearing cells occurs in the bursa Fabricius^1,2. Removal of the bursa at various times in the perinatal period^3–5 and/or administration of anti-μ chain antibodies have led to the postulate that IgM-bearing cells give rise in a sequential manner to cells with IgG and IgA on their surface⁶. Thus, administration of anti-μ to chicken embryos results in the elimination of cells bearing Ig of all classes, and in a depression in the synthesis of both IgM and IgG⁷. Administration of anti-μ to neonatal mice has also been shown to lead to a decrease in the serum level of all Ig classes, as well as a reduction of all Ig-bearing cells in the spleen, suggesting that the maturation sequence of Ig-bearing cells in birds and in mammals may be similar^8–10. Recent work by one of us (D.G.O.) has shown that in mice the bone marrow is a site of production and differentiation of Ig-bearing lymphocytes, suggesting that the bone marrow may be a mammalian equivalent of the bursa of Fabricius^11–13. The aim of the present investigation was to establish the distribution of lymphocytes bearing various Ig classes in the bone marrow of mice treated with anti-IgM, and compare it with that in normal bone marrow. The results indicate that anti-IgM injections prevent the development of lymphocytes bearing Ig of all classes in mouse bone marrow. In addition, most of the “null” small lymphocytes and many large lymphoid cells, hitherto found to be devoid of detectable surface Ig^11–14, are also eliminated