Isolation of macrophages; alveolar, peritoneal, Kupfer; macrophage phagocytosis assay; respiratory burst assays; antigen processing and presentation assay; bacterial uptake and killing by macrophages; bacterial models; MCMV host resistance model; parasite models; local lymph node assay; assessment of contact photo hypersensitivity using Langerhans cell enriched epidermal cells; assessment of the suppressor cell assay and its dissection; assays to evaluate pulmonary hypersensitivity; assessment of hypersensitivity by flow cytometry; autoimmunity - animal models.