Detection of immune complexes in sera of dogs with canine transmissible venereal sarcoma (CTVS) by a conglutinin-binding assay.

The canine transmissible venereal sarcoma (CTVS) is capable of extended growth in an allogeneic host. Since immune complexes can enhance allograft survival in other animal models, we used an enzyme-linked conglutinin-binding assay to determine the presence and amount of circulating immune complexes in dogs with CTVS. With the conglutinin-binding assay, 23 of 64 dogs (36 per cent) bearing CTVS had concentration of immune complexes 3 standard deviations greater than those detected in normal canine serum. When dogs with circulating immune complexes were separated into 3 groups based on whether the size of CTVS had increased (progressor), decreased (regressor) or remained the same (steady-state) during the week before collection of serum, no significant difference was found in the amounts of immune complexes in sera from progressor dogs. In 3 regressor dogs that received a second transplant of CTVS, the mean concentration of circulating immune complex was significantly greater than the mean for progressor dogs. In progressor dogs, amounts of immune complexes decreased with increasing tumour volume. Following sucrose density gradient ultracentrifugation analysis of sera from a normal and progressor dog, 27S complexes containing both IgG and IgM were detected in serum from a progressor dog. Thus, it appears that the conglutinin-binding assay is a useful and sensitive method for detecting immune complexes in canine serum.