Chronic ethanol induces inhibition of antigen-specific CD8+ but not CD4+ immunodominant T cell responses following Listeria monocytogenes inoculation.

Chronic ethanol consumption results in immunodeficiency. Previous work with chronic ethanol-fed mice has shown reduced splenic weight and cellularity, including reduced numbers of CD8+ T cells. However, antigen-specific CD8+ and CD4+ T cell responses in chronic ethanol-fed mice have been studied relatively little. We have used an attenuated Listeria monocytogenes strain DPL 1942 (LM DeltaactA) to inoculate mice and subsequently used CD4+ and CD8+ immunodominant peptides of LM to measure the CD4+ and CD8+ T cell responses after chronic ethanol exposure. We found no major differences between control and ethanol-fed mice in the kinetics and persistence of antigen-specific CD4+ T cells in response to an immunodominant LM peptide, as measured by intracellular IFN-gamma staining. In contrast to CD4+ responses, three methods of in vitro antigen presentation indicated that the primary response of CD8+ T cells to several different epitopes was reduced significantly in mice chronically fed ethanol. Antigen-specific CD8+ T cells were also reduced in chronic ethanol-fed mice during the contraction phase of the primary response, and memory cells evaluated at 29 and 60 days after inoculation were reduced significantly. BrdU proliferation assays showed that in vivo proliferation of CD8+ T cells was reduced in ethanol-fed mice, and IL-2-dependent in vitro proliferation of naive CD8+ T cells was also reduced. In conclusion, these results suggest that antigen-specific CD4+ T cell responses to LM are affected little by chronic ethanol consumption; however, antigen-specific CD8+ T cell responses are reduced significantly, as are in vivo and in vitro proliferation. The reduction of antigen-specific CD8+ T cells may contribute strongly to the immunodeficiency caused by ethanol abuse.

A practical method of chronic ethanol administration in mice.

Mice provide a useful model for the study of immune deficiency caused by chronic alcohol abuse. Their suitability is related to several factors, including in particular the extensive knowledge base in the immunology of mice already existing in the literature. Specific modeling of the immunodeficiency of the chronic human alcoholic requires that ethanol must be administered to the model for a significant portion of its life span. In mice, it has proven to be necessary to administer ethanol daily for up to 32 wk or longer to observe all the immune abnormalities that occur in middle-aged alcoholic humans. Such time spans are problematic with many of the common protocols for ethanol administration. It has been shown by others and confirmed by our group that the most practical way of accomplishing such long protocols is by administering ethanol in water as the only choice of water. Details of management of the chronic ethanol mouse colony are described here that are necessary for the success of such studies, including methods for initiating ethanol administration, maintenance of barrier protection, monitoring weight gain, strain differences and fetal alcohol exposure.

Polyclonal and antigen-specific responses of T cells and T cell subsets.

Evaluation of the functional responses of T cells is of importance in determining the mechanism(s) of immunodeficiency resulting from chronic alcohol abuse and other conditions that lead to immune dysfunction. Mice that are chronically exposed to 20% (w/v) ethanol in water develop immunodeficiency and have T cells with abnormal activation profiles, reduced total numbers, increased CD4/CD8 ratios, and an increased memory/naïve phenotype ratio. These cells also have abnormal antigen-specific responses after inoculation of the ethanol mice with model infectious organisms. Study of the functional abnormalities of these cells requires a reliable system that can present appropriate activation stimuli in vitro for the generation of polyclonal or antigen-specific responses in enriched or purified T cells, free of the influence of previously ethanol exposed accessory cells. In this chapter, we describe protocols to assess the T cell response to polyclonal stimulation through the T cell receptor and the use of a model infectious disease bacterium, Listeria monocytogenes, that allows evaluation of the T-cell response to specific peptide epitopes of the bacterium after previous inoculation.

The TGF-beta response to Leishmania chagasi in the absence of IL-12.

Cure of leishmaniasis requires a type 1 immune response characterized by IFN-gamma production. Leishmania major infection leads to a type 2 response suppressing cure of susceptible BALB/c mice, and L. major causes an exacerbated type 2 response in mouse strains with a gene knockout (KO) such that they lack IL-12p40 (IL-12KO mice). In contrast, type 1 responses are inhibited by TGF-beta without Th2 cell expansion in BALB/c mice infected with L. chagasi. We questioned whether the type 2 or the TGF-beta response would dominate during L. chagasi infection of IL-12KO mice. C57BL/6 mice developed self-resolving L. chagasi infection with abundant IFN-gamma. In contrast, L. chagasi disease was exacerbated and IFN-gamma was low in IL-12KO mice. Total TGF-beta was significantly higher in IL-12KO than control C57BL/6 mice, but IL-4 and IL-10 levels were similar. TGF-beta was further augmented in IL-12/IFN-gamma double-KO mice. Thus, in contrast to L. major, the TGF-beta response was exacerbated whereas type 2 cells were not expanded during L. chagasi infection of IL-12KO mice. We conclude that L. chagasi has an inherent propensity to elicit a prominent TGF-beta response that either suppresses, or is suppressed by, a type 1 response. We propose this be termed a "type 3" immune response, which can antagonize a type 1 response.