Isabelle Millet

Opposite effects of the catecholamines dopamine and norepinephrine on murine polyclonal B-cell activation.

The effects of dopamine (DA) and norepinephrine (NE) on polyclonal B-cell activation induced in vitro by lipopolysaccharide (LPS) and on cyclic AMP response in BALB/c mouse lymphocytes were investigated. DA at non-cytotoxic concentrations (5 x 10(-5) M and 10(-4) M) inhibited, but NE (5 x 10(-6) M to 5 x 10(-5) M) enhanced LPS-stimulated proliferation and Ig synthesis by lymphocytes from spleen, mesenteric lymph nodes and Peyers patches. Depletion of adherent cells and T lymphocytes did not prevent the respective effects of DA and NE, and the drug effects were reproduced on nude (nu+/nu+) spleen cell proliferation and differentiation stimulated by LPS. The inhibitory effect of DA persisted even if the drug was added as late as 48 h after the mitogen. In contrast, NE was no longer stimulatory if added 2 h later than LPS. The effect of DA was blocked neither by DA1 or DA2 dopaminergic antagonists (SCH 23390 and sulpiride respectively), nor by alpha- or beta-adrenoceptor antagonists (phentolamine and propranolol respectively). Enhancement by NE was antagonized by propranolol, but not by phentolamine. Both DA and NE raised the level of cyclic AMP in unfractionated spleen cells as well as in B-enriched spleen cells but DA was less potent than NE. Pre-incubation of spleen lymphocytes with LPS for 1-24 h did not alter their cyclic AMP response to NE but it prevented the loss of sensitivity to DA after 4 or 24 h of in vitro incubation. The lysosomotropic agent chloroquine induced suppression of LPS-stimulated proliferation and Ig production with a dose-response profile similar to that of DA. Altogether, these results indicate that the catecholamines can exert opposite effects on polyclonal B-cell activation by acting directly on B lymphocytes.

Induction of Murine B Cell Proliferation and Immunoglobulin Synthesis by Some Bacterial Ribosomes

Ribosomal preparations from Klebsiella pneumoniae, Haemophilus influenzae, Streptococcus pyogenes, and Streptococcus pneumoniae were investigated with respect to their activating capacity towards murine lymphoid cells. The proliferation of BALB/c spleen cells was induced in a dose‐dependent fashion (from 1 to 100 μg/ml) by ribosomes of K. pneumoniae, H. influenzae, and S. pyogenes with a peak activity at 48 or 72 hr of culture. The majority of the blast cells induced by these ribosomal preparations were positive for surface‐immunoglobulin (S‐Ig) and negative for Thy 1.2. Furthermore, K. pneumoniae, H. influenzae, and S. pyogenes ribosomes induced the synthesis of IgM and some IgA. Cell proliferation and induction of IgM production were also demonstrated with the 3 ribosomal preparations using spleen cells from athymic nude (nu+/nu+) mice, Lyb‐5‐defective CBA/N spleen cells, B cell‐enriched and T cell‐depleted BALB/c spleen cell suspensions, as well as spleen cells from the Ips gene‐deficient C3H/HeJ strain. Cell culture supernatants contained specific anti‐ribosome IgM antibodies. Antibodies of other specificities (anti‐sheep erythrocytes) were also demonstrated in supernatants from K. pneumoniae‐stimulated cultures. Evidence against a possible role of contamination of K. pneumoniae and H. influenzae ribosomes by lipopolysaccharide‐ or lipid A‐associated proteins in this effect is discussed. Ribosomes from S. pneumoniae did not induce 3H‐thymidine incorporation nor Ig production. None of the 4 ribosomal preparations was found to stimulate T cell blastogenesis or to induce interleukin‐2 production by naive BALB/c spleen cells. Finally, ribosomes from H. influenzae, S. pyogenes, S. pneumoniae but not those of K. pneumoniae stimulated interleukin‐1 production by adherent spleen cells, from BALB/c mice.

Proliferative Response of Human T Lymphocytes to a Vaccinal Preparation of Ribosomes from Streptococcus pyogenes

The in vitro lymphocyte-activating properties of a ribosomal preparation of Streptococcus pyogenes were investigated. The preparation was mitogenic for human lymphocytes with a peak of 3H-thymidine incorporation occurring after 3-5 days of culture. The response was abolished by removal of CD3-positive cells and by alteration of accessory cells by exposure to L-leucine methyl ester. Most of the cells synthesizing DNA at the end of the culture expressed CD4 or CD8 but not CD20 antigens. No immunoglobulin synthesis was demonstrable. Although the same preparation was shown to be a T-independent polyclonal B-cell activator of murine cells, it preferentially triggers T cells in humans.

Suppression of Human IgA-B-Cell Maturation by IgA-Binding Factors Requires T Cells

IgA-binding factors (IgA-BFs) prepared from human peripheral blood mononuclear cells selectively decrease the generation of cytoplasmic IgA-positive cells in peripheral blood mononuclear cell cultures stimulated by pokeweed mitogen or by Nocardia opaca delipidated cell mitogen. In N. opaca delipidated cell mitogen stimulated cultures, the suppressive effect of IgA-BFs was no longer demonstrable after removal of sheep erythrocyte rosetting T cells or after depletion of CD8+ cells, but it was not altered by depletion of CD4+ cells. In pokeweed mitogen stimulated cultures of T-depleted peripheral blood mononuclear cell suspensions, IgA-BFs were ineffective when irradiated (12 Gy) instead of control T cells were used for reconstitution. The data indicate that radiosensitive and CD8+ T cell subsets may be required for IgA-BFs to suppress the generation of IgA-containing B cells after polyclonal activation of human peripheral blood mononuclear cells.