thymosin and Hypersensitivity

Thymosin alpha1 (Talpha1), first described and characterized by Allan Goldstein in 1972, is used worldwide for the treatment of some immunodeficiencies, malignancies, and infections. Although Talpha1 has shown a variety of effects on cells and pathways of the immune system, its central role in modulating dendritic cell (DC) function has only recently been appreciated. As DCs have the ability to sense infection and tissue stress and to translate collectively this information into an appropriate immune response, an action on DCs would predict a central role for Talpha1 in inducing different forms of immunity and tolerance. Recent results have shown that Talpha1: (a) primed DCs for antifungal Th1 resistance through Toll-like receptor (TLR)/MyD88-dependent signaling and this translated in vivo in protection against aspergillosis; (b) activated plasmacytoid DCs (pDC) via the TLR9/MyD88-dependent viral recognition, thus leading to the activation of interferon regulatory factor 7 and the promotion of the IFN-alpha/IFN-gamma-dependent effector pathway, which resulted in vivo in protection against primary murine cytomegalovirus infection; (c) induced indoleamine 2,3-dioxygenase activity in DCs, thus affecting tolerization toward self as well as microbial non-self-antigens, and this resulted in vivo in transplantation tolerance and protection from inflammatory allergy. Talpha1 is produced in vivo by cleavage of prothymosin alpha in diverse mammalian tissues. Our data qualify Talpha1 as an endogenous regulator of immune homeostasis and suggest that instructive immunotherapy with Talpha1, via DCs and tryptophan catabolism, could be at work to control inflammation, immunity, and tolerance in a variety of clinical settings.

Topics: Acquired Immunodeficiency Syndrome; Animals; Aspergillosis; Dendritic Cells; HIV Infections; Homeostasis; Humans; Hypersensitivity; Immunity, Innate; Inflammation; Mycoses; Neoplasms; Signal Transduction; Th1 Cells; Thymalfasin; Thymosin; Thymus Gland

There is a large body of evidence for the role of thymosin peptides in immunogenesis and immunity. In this paper we report on the influence of prothymosin alpha 1 (ProT-alpha 1), a hormone-like peptide derived from the calf thymus, on humoral and cellular immune reactions in the rat. Young adults received intraperitoneal injections of ProT-alpha 1 in the periods before and after immunization with cellular and soluble antigens. ProT-alpha-treatment produced a dose-dependent increase of both humoral and cell-mediated immune responses. The thymus weight increased but not that of spleen. Treatment of nonimmunized rats with this polypeptide significantly elevated the number of CD4+ and decreased the number of CD8+ cells in the peripheral blood. The results suggest a potent immunostimulatory activity of ProT-alpha 1 and imply direct action of this polypeptide on T lymphocytes.

Topics: Adjuvants, Immunologic; Animals; Antibodies, Monoclonal; Antibody Formation; Arthus Reaction; Blood Cell Count; Body Weight; CD4 Antigens; CD8 Antigens; Erythrocytes; Hemolytic Plaque Technique; Hypersensitivity; Hypersensitivity, Delayed; Immunity, Cellular; Lymphocytes; Male; Organ Size; Protein Precursors; Rats; Rats, Inbred Strains; Sheep; Thymosin

Topics: Animals; Dioxins; Drug Hypersensitivity; Endotoxins; Female; Hypersensitivity; Immunosuppressive Agents; Listeriosis; Mice; Nitroblue Tetrazolium; Oxidation-Reduction; Polychlorinated Dibenzodioxins; Thymosin; Thymus Hormones; Zinc