title: Secondary immunity to Legionella pneumophila and Th1 activity are suppressed by delta-9-tetrahydrocannabinol injection.
abstract: Resistance to infection with Legionella pneumophila is primarily dependent upon cell-mediated immunity rather than humoral immunity. Recent evidence suggests that activation of cell-mediated immunity depends on Th1 cells and activation of humoral immunity depends on Th2 cells. In this report, delta 9-tetrahydrocannabinol (THC), the major psychoactive cannabinoid of marijuana and an immunomodulator, suppressed development of secondary immunity to L. pneumophila, which correlated with a reduction in Th1 activity. BALB/c mice, infected with a primary sublethal dose of L. pneumophila, developed resistance to a larger challenge infection 3 to 4 weeks later. However, intravenous injection of THC (4 mg/kg of body weight) 1 day prior to primary infection resulted in increased mortality after the challenge infection. The level of anti-L. pneumophila antibodies in serum increased in both THC-treated and control mice; however, in the THC group IgG1 antibodies which are stimulated by Th2 cells were elevated while Th1-regulated, IgG2a antibodies were depressed. Furthermore, cultured splenocytes from THC-treated mice had less L. pneumophila-specific lymphoproliferation, indicating a deficiency in cell-mediated immunity. Normal mouse splenocytes treated in vitro with THC and pokeweed mitogen showed suppressed production of gamma interferon, a cytokine associated with Th1 cells, but increased production of interleukin 4, a cytokine produced by Th2 cells. Splenocytes from THC-treated mice, stimulated in vitro with either pokeweed mitogen or anti-CD3 antibodies, also produced less gamma interferon, indicating less Th1 activity in these mice. These results suggest that THC decreases the development of anti-L. pneumophila immunity by causing a change in the balance of Th1 and Th2 activities.
authors.affiliation: Department of Medical Microbiology and Immunology, University of South Florida College of Medicine, Tampa 33612.
authors.forename: C A
authors.initials: CA
authors.lastname: Newton
authors.forename: T W
authors.initials: TW
authors.lastname: Klein
authors.forename: H
authors.initials: H
authors.lastname: Friedman
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D013759:Dronabinol / Q000494:pharmacology*; D005260:Female; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007371:Interferon-gamma / Q000096:biosynthesis; D016952:Legionella pneumophila / Q000276:immunology*; D007877:Legionnaires' Disease / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D006377:T-Lymphocytes, Helper-Inducer / Q000187:drug effects* / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D007166:Immunosuppressive Agents; D013759:Dronabinol; D007371:Interferon-gamma