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An increase in attachment of SRBCs to Procambarus clarkii hemocytes has been shown after the crayfish were injected with a live or killed Pseudomonas strain RS2b. The increase in attachment occurred at 8 hours post injection and peaked at 24 hours for both experimental groups. The population of hemocytes with receptors for LPS and mannose also increased at 8 hours post injection and peaked at 24 hours for both experimental groups. At 96 hours post injection the number of receptor bearing hemocytes and hemocytes bound to SRBCs began to decrease to the level of the control for both groups. The protein concentration of hemolymph from the experimental groups remained stable at 8 and 24 hours post injection and increased at 96 hours. The correlation of the protein concentration increase at 96 hours with the decrease of receptor bearing hemocytes may be due to the degranulation of the receptor bearing hemocytes.

Procambarus clarkii hemocytes have been shown to bind to both LPS and a mannose containing neoglycoprotein conjugated to fluorescent probes. A decrease in the observed number of fluorescent hemocytes indirectly indicated that the binding of FITC-LPS to these cells is impaired by initial incubation with LPS. Prior treatment of hemocytes with horseradish peroxidase, a mannose rich glycoprotein, decreased their capacity to bind mannose. Mannan had no inhibitory effect on the binding of either ligand. Mixed hemocytes and hemocyte subpopulations separated by buoyant density were incubated with both ligands and revealed that a subpopulation of granular hemocytes bound both LPS and mannose. These results suggest the possible presence of two different pattern recognition cell surface receptors on this subpopulation of granular hemocytes from the red swamp crayfish, Procambarus clarkii, which may specifically recognize and bind to both LPS from gram-negative bacteria and to mannose containing glycoproteins found on microbial surfaces.