Figure 4. Treatments greatly increased titers of antibodies to the constructs used for therapy but reduced or had little effect on titer to rat muscle AChRs.

These are the rats used in Fig 2 and 3. Sera of individual rats from 6 rat groups were collected 7 weeks after the induction of EAMG. (A) Antibody titer to rat muscle AChR was evaluated by immunoprecipitation of AChRs labeled with 4 nM ¹²⁵I-αBgt. Treatment with 5 mg doses of the subunit mixture reduced autoantibody titer by half, while treating with 1 or 2 mg doses had no significant effect on the titers. Control therapy with 5 mg doses of OVA, which resulted in no clinical benefit, also decreased antibody titer to rat muscle AChR by half. The other control therapy, with 5 mg doses of <1-ECD, had no effect on autoantibody titer. Thus, antibody titer to rat muscle AChR, including antibodies to extracellular and cytoplasmic domains, was not correlated with the clinical state of the rats. Rats immunized with OVA, but not Torpedo AChR, then treated i.p. with 5 mg doses of the AChR subunit mixture, developed very low titers to rat muscle AChRs (less than 10% of that of the EAMG control rats). (B) Antibody titers to the subunit mixture (open bar) and to the <1-ECD (closed bar) were evaluated by ELISA assays. Untreated EAMG, as expected, resulted in some titer to both antigens. Treatment of EAMG with i.p. OVA had little effect on these titers. Therapies with either the subunit mixture or the <1-ECD greatly increased antibody responses to the constructs used for therapy. Rats immunized with ovalbumin, but not Torpedo AChR, then treated i.p. with subunits, developed low titers to the subunit mix, but no detectable response to <1 extracellular domain. This indicates that those antibodies from rats treated with the subunit mixture were primarily directed against cytoplasmic domains.