Studies in T cellC (2C4) and IFN-Cdeficient (5) mice have confirmed the critical requirements for these elements in host immunity. T cells could mature into IFN-Cor IL-4Csecreting T helper cells, respectively, even when antigen presentation was suboptimal or antigen dose was submitogenic. These experiments demonstrate that activation of T helper cells to a threshold required for IL-2 production or proliferation is not required to achieve induction of disease-regulating T helper cell effector functions, and that pathogen-associated secondary activation signals may facilitate the full differentiation of T helper subsets during limiting presentation of antigenic peptides. Experimental contamination of inbred strains of mice with remains an exceptional model for analysis of CD4+ subset differentiation in vivo (1). Control of disease is dependent on class IICrestricted Th type 1 (Th1) cells and their production of IFN- which is required to activate macrophages to restrain intracellular replication of the organism. Studies in T cellC (2C4) and IFN-Cdeficient (5) mice have confirmed the crucial requirements for these Pimonidazole elements in host immunity. MHC class IICdeficient mice from a genetically resistant background are completely susceptible to contamination (6, 7), while MHC class ICdeficient mice from a genetically resistant background retain resistance to contamination (8). In EM9 contrast to most strains of mice, BALB animals are unable to contain due to the development of an aberrant Th type 2 (Th2) response during contamination. The absence of class I does not impact Th2 development or susceptibility in BALB/c mice (9). replicates productively only in host macrophages within an endolysosomal-like compartment that contains MHC class II molecules, some of which are devoid of invariant chain (10, 11). Contamination of macrophages in vitro is usually associated with diminished MHC class IICdependent presentation of exogenous antigens (12, 13). Although it is usually unclear whether this is due to degradation or improper trafficking of MHC class II/peptide complexes from your parasitophorous vacuole (14), qualified MHC class II molecules reach the cell Pimonidazole surface as exhibited by immunofluorescent, functional, and biochemical studies (12, 13, 15). Since invariant chain is usually involved in both targeting newly synthesized MHC class II molecules to peptide-generating compartments, and in protecting the peptide cleft during transit from your endoplasmic reticulum (16), we expected significant impairment in host immune responses to using invariant chainCdeficient (Ii ?/?) mice. Unexpectedly, both Th1 and Th2 responses were managed in mice on genetically resistant or susceptible backgrounds, respectively, emphasizing the Pimonidazole capacity of the immune system to sustain T cell effector development even under conditions of suboptimal activation. Materials and Methods Mice. Ii ?/? mice (17), class II ?/? mice (18), 2m ?/? mice (19), BALB/c (Jackson Laboratory, Bar Harbor, ME), and C57BL/6 (Jackson Laboratory) mice were bred and maintained in the Pimonidazole University or college of Chicago animal facilities. Double mutant Ii ?/? 2m ?/? mice were generated by interbreeding. Mice were screened by fluorescent cytometry using appropriate monoclonal antibodies for levels of MHC class I, class II, CD4+ and CD8+ T cells to confirm genotypes. Most mice used in these experiments were fourth generation C57BL/6, or fourth generation BALB/c. Mice on a 129 C57 ((20), were established using standard methods, and are characterized elsewhere (Reiner, S., manuscript in preparation). T cells from these mice identify an 18Camino acid peptide epitope restricted by I-Ad from an immunodominant antigen, Leishmanial receptor for activated protein kinase (LACK)1, that is expressed in both the promastigote and amastigote forms of the parasite (21). Thymic selection but not peripheral activation, of the transgene clonotype occurs around the mismatched.
