Immunologic recognition of microbial pathogens is fundamental for fighting infectious disease. Our major goal is to understand the interaction and neutralization of foreign antigens by the immune system through high-resolution x-ray structural studies of antibodies, Variable Lymphocyte Rectors (VLRs) and antigens in the humoral system, T-cell receptor complexes with MHC class I and class II in the cellular system, and through pattern recognition receptors, such as TLRs, in the innate immune system.