Ia ANTIGENS ON MURINE LYMPHOID CELLS: DISTRIBUTION, SURFACE MOVEMENT AND PARTIAL CHARACTERIZATION*

Abstract

SUMMARY Antisera directed against the I (immune response gene) segment of the murine major histocompatibility complex were prepared, and the distribution of lymphoid cells binding the antisera studied by radioautography. A clear bimodal distribution of grain counts was observed in lymph node and spleen. Bone marrow lymphocytes showed heavy but heterogeneous labelling, while thymocytes were lightly but definitely labelled. Approximately 30% of lymph node cells and 60% of spleen cells were heavily labelled. The heavily labelled cells were shown to be B cells. Ia antigens are present on plaque forming cells, but probably in smaller amounts than on resting B cells. One plasma cell tumour was studied, and was found to possess little or no Ia antigen. There was no demonstrable labelling of thoracic duct lymphocytes from preparations of T cells activated to histocompatibility antigens. However, several T cell lymphomas probably possess Ia antigens, since they were rejected when transplanted into mice differing at the I region. Overall, the data indicate that Ia antigens are expressed on at least some T cells. The Ia antigens were shown to move independently of surface immunoglobulin on B cells, demonstrating the non‐identity of these molecules. Pretreatment of B cells with anti‐immunoglobulin did not inhibit binding of anti‐Ia sera. The Ia antigens could be capped by a sandwich technique in 75% of labelled cells. The Ia antigens were specifically precipitated from lysates of surface radioiodinated spleen cells, and the products analysed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. A single specific peak of radioactivity corresponding to a molecular weight of approximately 30,000 was found. The significance of these results in relation to immune response genes, receptors for antigen on T cells, and receptors for the Fc portion of IgG on B cells, is discussed.

Independent regulation of IgM, IgD, and Ia antigen expression in cultured immature B lymphocytes.

“…4 shows two-color FACS analysis in which splenic cells from either 2-wk-old mice or adult mice were simultaneously stained with antibodies against Ia and IgM or Ia and IgD. As reported previously (35,36), adult sIg + cells are found to also express Ia. In contrast, in the young spleen, a sizable population of cells that express IgM appear to lack expression of Ia ( Fig.…”

Ly and Ia antigen phenotypes of T cells involved in delayed-type hypersensitivity and in suppression.

“…Ia antigens, although most densely represented on B cells (18), have been detected in small quantities on some T cells (19)(20)(21). Despite this meager representation, treatment with anti-Ia serum and C has been shown to inhibit certain T-cell functions.…”

A Receptor for Antibody on B Lymphocytes

“…The reagents, F/G and rabbit IgG anti-mouse IgG were iodinated by the chloramine T method as described by G reenwood et al [14] and anti-la IgG by the method of G oding et id. [13]. The procedure was car ried out to produce the following specific activities: for F;.G 40-50 «Ci//tg, for rab bit IgG anti-mouse IgG 12-15 «Ci/ng and for anti-la IgG 2 /<Ci//tg.…”

“…Preparation of anti-la serum. Anti-la serum (K haplotype) was a gift from Dr. J. G oding and prepared by the method of G oding et al [13]. A.TH mice were inject ed 4 times intraperitoneally with a mixture of 2X10" A.TL thymocytes and 6X105 A.TL lymph node cells at weekly intervals followed by monthly booster injections until high cytotoxic titres were obtained.…”