Permeability studies on taeniid metacestodes: II. Antibody-mediated effects on membrane permeability in larvae of Taenia taeniaeformis and Taenia crassiceps.

Incubation in immune rat serum (IRS) was shown to increase the rate of absorption of 125I RNase-A but not 125I BSA by larvae of Taenia taeniaeformis and T. crassiceps. This effect required a heat labile factor in serum, and partial activity could be restored in heat-treated IRS by adding normal rat serum (NRS) as a source of complement. In addition, the effectiveness of IRS in altering permeability was shown to be dependent on the concentration of functional complement. Both live and dead larvae incubated in NRS rapidly depleted hemolytic complement levels in the surrounding medium. Immunoglobulin fractions from IRS separated by anion exchange chromatography and and gel filtration were tested in the presence of excess complement for their ability to affect uptake of 125I RNase-A. Enhanced permeability was observed in larvae incubated in each fraction. The results show that antibodies in conjunction with complement are capable of disrupting larval permeability control in vitro. The observation that larvae were able to restore normal control as complement levels declined suggests that the parasites may overcome this immunologic effector mechanism by interfering with complement function.