Some mosquito species or strains serve as disease-vectors while others- even highly similar others-do not. My long-term objective is to characterize hemocyte proteins that determine whether a mosquito can be a disease vector. We have previously generated monoclonal antibodies against M. sexta hemocytes and I will use these as probes to study A. aegypti hemocytes. This project's aim is to identify similarities between Manduca sexta and Aedes aegypti cell-based immune responses and to characterize hemocyte proteins involved in these responses. The project's specific aims are to: 1. Identify antigens common to M. sexta and A. aegypti hemocytes. Monoclonal antibodies against M. sexta hemocytes will be used in immunofluorescence microscopy of A. aegypti hemocytes. Those monoclonal antibodies positive for both species will be further tested to see if they bind hemocyte antigens that differ in abundance or distribution during an immune response in: (i) E. coli-inoculated compared to non-inoculated M. sexta; (ii) D. immitis-inoculated compared to control-inoculated A. aegypti. (iii) E. coli-inoculated compared to control-inoculated A. aegypti. 2. Purify and characterize two hemocyte antigens (proteins), from M. sexta, identified in the above tests. 3. Clone and sequence the M. sexta cDNAs for these two proteins. Ultimately I wish to use these cDNAs as probes for similar sequences in the mosquito. These results will contribute to our understanding of insect immunity and possibly provide insight into the development of new methods of insect disease vector control.