Sheathed and unsheathed microfilarial surfaces, interactions with host serum proteins in diethylcarbamazine

There is no question that when a high titer of antibodies specific for microfilaria (mf) surfaces is present in assays of granulocyte adherence that cell binding is greater than in normal serum. It is also well documented that complement intact serum with or without surface specific antibody permits the deposition of C3 on mf, and surface bound C3b is known to facilitate adherence by granulocytes and especially eosinophils. How diethylcarbamazine enhances cell adherence to mf surfaces directly or as mediated by specific antibody, complement or as yet untested serum components such as eosinophil granule major basic protein (MBP) remains unknown. In reviewing work which has attempted to investigate this question, it was found that there were several possible sources of inconsistencies in the reagents usually employed in the cell adherence experiments with mf and some of these may have already contributed to confusion in the interpretation of results reported to date. Firstly, eosinophils collected from individuals with high eosinophil counts appear to be more reactive than those from normal donors. Secondly, Brugia pahangi mf taken in early patent infections or from very high microfilaremic infections in cats are less reactive with granulocytes than those from more long-term infections and this may be related to the differences in surface carbohydrate composition detected among mf taken from uteri of adult females, in vitro released mf and mf collected from host tissue. Thirdly, higher levels of MBP may be present in serum from individuals with high eosinophil counts associated with filarial infection than in serum from normal controls.