A flow cytometric approach to identifying the relative abundance and functional capacities of hemocyte subsets in the American cockroach, Periplaneta americana (L.)

There is growing interest in insects as subjects for comparative immunological studies; however, very little has been done to wholistically characterize insect immune cells using modern techniques such as flow cytometry, and virtually no work of this kind has been done in Periplaneta americana. Here, we use an array of general molecular probes including fluorescent lectins, lysosomal indicators, and functional assays to distinguish and characterize insect immune cells (hemocytes) based on cell markers and functions. We have utilized fluorescent tracers of lysosomal content, ROS production, and phagocytosis, as well as microscopic examination of morphology and melanization to distinguish hemocyte types based on these functions. Our findings support the use of lectins as an additional means of separating at least three populations of cockroach immune cells coupled with morphological measurements such as size and complexity. Our results indicate that many functions are enriched in the more granular hemocyte population as these are the cells that undergo phagocytosis and melanization.