Different expression of the recombination activity gene RAG-1 in various populations of thymocytes, peripheral T cells and gut thymus-independent intraepithelial lymphocytes suggests two pathways of T cell receptor rearrangement.

The presence of transcripts of the recombination activating gene RAG-1 was studied by in situ hybridization on selected populations of murine thymocytes, peripheral lymphocytes and gut intraepithelial lymphocytes (IEL), obtained by cell sorting. RAG-1 mRNA was found in a majority of "double-positive" (DP) thymocytes, but was absent in "single-positive" thymocytes and peripheral T lymphocytes. The only other T lineages in which about 10%-20% of the cells contained RAG-1 mRNA, and in smaller amounts, were "double-negative" (DN), T cell receptor (TcR) gamma delta- cortical thymocytes and gut CD3- IEL.

Cytotoxic differentiation of mouse gut thymodependent and independent intraepithelial T lymphocytes is induced locally. Correlation between functional assays, presence of perforin and granzyme transcripts, and cytoplasmic granules.

Mouse gut intraepithelial lymphocytes (IEL), whether thymodependent (CD4+ or CD8 alpha/beta +; TCR-alpha/beta +) or thymoindependent (CD8 alpha/alpha +; TCR-alpha/beta + or -gamma/delta +), all display cytotoxic activity in a "redirected lysis assay" using anti-CD3 or anti-TCR beta or delta chains secreting hybridomas as targets; this is also observed with IEL of germ-free mice, indicating that this activity, which is absent in peripheral T lymphocytes, does not require stimulation by bacterial antigens. Perforin and granzyme transcripts are detectable in unselected gut IEL, in contrast to normal T lymphocytes of peripheral lymphoid organs. Cytological labeling (with [3H]DFP) of IEL smears reveals labeled granules (i.

Two gut intraepithelial CD8+ lymphocyte populations with different T cell receptors: a role for the gut epithelium in T cell differentiation.

Mouse gut intraepithelial lymphocytes (IEL) consist mainly (90%) of two populations of CD8+ T cells. One bears heterodimeric alpha/beta CD8 chains (Lyt-2+, Lyt-3+), a T cell receptor (TCR) made of alpha/beta chains, and is Thy-1+; it represents the progeny of T blasts elicited in Peyer's patches by antigenic stimulation. The other bears homodimeric alpha/alpha CD8+ chains, contains no beta chain mRNA, and is mostly Thy-1- and TCR-gamma/delta + or -alpha/beta +; it is thymo-independent and does not require antigenic stimulation, as shown by its presence: (a) in nude and scid mice; (b) in irradiated and thymectomized mice repopulated by T-depleted bone marrow cells bearing an identifiable marker; (c) in thymectomized mice treated by injections of monoclonal anti-CD8 antibody, which lead to total depletion of peripheral CD8+ T lymphocytes; and (d) in germ-free mice and in suckling mice.

Receptor-mediated phagocytosis by macrophages induces a calcium-dependent transient increase in c-fos transcription.

The transcription of the c-fos gene and the level of c-fos mRNA in mouse peritoneal macrophages are rapidly, strongly and transiently increased after Fc- and C3b-mediated phagocytosis, but not after phagocytosis of latex particles. In order to induce both phagocytosis and a rise in c-fos mRNA, binding to receptors must be followed by mobilization of Ca++ from intracellular Induction of c-fos transcription in macrophages by other agents acting through different intracellular "messengers', i.e.

Structural differences between heavy chains of secreted and membrane-bound IgM of a human lymphoblastoid cell line.

The human lymphoblastoid cell line BL was shown to synthesise three distinct molecular species of immunoglobulin M heavy chains: membrane-bound (micrometer). intracellular (micro i) and secreted (microseconds) micro-chains. Only the membrane-bound form could be labeled with a lipophilic photoactivatable nitrene reagent.