The cored sponge model of in vivo leucocyte chemotaxis

A method has been developed for the in vivo measurement of leucocyte chemotaxis in response to the bacterial chemotactic peptide F-met-leu-phe (FMLP). Polyurethane sponges were pre-treated with FMLP and implanted subcutaneously in rats and after a suitable interval removed for determination of leucocyte influx. In vivo concentration gradients of chemotactic factors within intact sponges were shallow and leucocyte accumulation unsatisfactory. Accordingly a cored sponge model was developed in which the cylindrical core only was treated with chemotactic factor and the sponge reassembled prior to subcutaneous implantation. Steep concentration gradients were established within the outer sponge matrix with marked effects on leucocyte accumulation, permitting studies of the time course of in vivo chemotaxis. With cored sponges test to control cell number ratios were maximal at 4 hours using both free and albumin-bound FMLP. This model of in vivo chemotaxis may prove useful in several areas of inflammation research.