We will study the "initiation" of the elicitation of T cell mediated immunity in vivo. We have discovered that the initiation of elicitation is due to a series of processes. We postulate that these processes begin within hours after sensitization. We postulate that within 1-hr of immunization there is activation of Valpha14+ Jalpha18+ CD1d-restricted NKT cells. The NKT cells produce IL-4 to co-activate the Beta-1 Beta cell subset to produce initiating IgM antibodies. This, leads via local complement C5a activation of mast cells, to the local recruitment of effector T cells to the site of Ag challenge. These initiating processes occur in the murine model of allergic contact dermatitis, and in a related model of occupational asthma involving hapten elicitation of airway hyperreactivity (AHR) within 1-day of immunization. AHR similarly is postulated to depend on an early process mediated by NKT cell stimulated Beta-1 cell mediated C5a generation. Our focus in this proposal is the induction of CS-initiating Beta-1 cells. We propose this is due to prior rapid activation of NKT cells, perhaps via release endogenous glycolipid antigens, within hours post-contact immunization, to produce IL-4 that co-activates the Beta-1 cell, to produce the initiating IgM antibodies. Taken together, these studies extend the study of CS-initiation to induction of the mediating Beta-1 cells, potentially activated via NKT cell IL-4, and extend these concepts to mouse models of occupational medicine. Specific Aim #1: We will determine whether NKT cells are essential in CS, how they are activated, and if the NKT cells function in the initiation of CS by potentially producing IL-4. Specific Aim #2: We will determine if and how Beta-1 cells are activated by IL-4 early in the induction of CS, and whether IL-4, acting via STAT-6 signaling is essential, and how the Beta-1 cells may possibly migrate to lymph nodes and then to produce circulating CS-initiating IgM antibodies by only 1-day post-immunization. Specific Aim #3: In a hapten induced murine model of occupational asthma, we will determine the potential role of NKT cells in the production of B-1 cell derived IgM antibodies, that mediate C5a-dependent airway hyperreactivity (AHR); just 1-day post-immunization; and the mechanisms of the induced AHR.