Experimental allergic neuritis: effect of plasma infusions.

The effect of intravenous fresh frozen plasma (FFP) and artificial plasma infusions upon the clinical course of chronic experimental allergic neuritis (EAN) in the rabbit was investigated. A total of 12 animals allocated to treatment groups received rabbit FFP or a gelatin plasma expander Haemaccel (Hoechst) and were compared to 13 control non-treated animals. Animals receiving Haemaccel at a rate of 15 ml/kg/day for 7 days showed no significant clinical benefit at any stage. However, animals receiving 15 ml/kg/day FFP for 8 days showed significant clinical benefit during treatment initiated at the onset of definite neurological symptoms of EAN (Mann-Whitney U test, day 4 post-allocation P less than 0.05; day 6 post-allocation P less than 0.01; day 8 post-allocation P less than 0.05). Relapse was observed after cessation of treatment such that comparisons of clinical scores at day 14 and 22 post-allocation revealed no significant differences. Analysis of plasma anti-myelin IgG levels by ELISA showed that non-immunogenic plasma volume expansion decreased anti-myelin IgG concentrations immediately by an average of 34% but had no long-term effect. In contrast, anti-myelin IgG concentrations in FFP infused animals were significantly decreased, compared to controls, when measured 24 h after the last infusion (Student's t-test P less than 0.05). Identical percentage weight losses for both control and treatment groups post-allocation indicated that this decrease was immunologically mediated and not due to plasma dilution. Similar plasma cortisol concentrations measured in both groups showed no significant artifactual induction of endogenous steroid production. Infusions of FFP during early disease progression are able to mediate clinical remission in animals with chronic EAN.