Circulating immune complexes in murine neuroblastoma: quantification and shifts in immunoglobulin composition

Circulating immune complexes (CIC) in sera obtained from neuroblastoma (NB)-bearing A/J mice were quantitated using a modified conglutinin (Kg) RIA technique which--in this case--gives very reproducible results. It shows that CIC levels in these sera increase almost linearly as a function of time after tumor challenge. Three weeks after inoculation values ranging from about 4 to up to 10 times those of normal sera are obtained, depending on the type of inoculum (NB tumor or established NB cell lines). However, when tumor is adapted to cell culture, these CIC levels, measured at a constant time interval after challenge, decrease on continued subcultivation in vitro. Furthermore, analyses of the immunoglobulin classes involved in the complexes show that this decrease is more pronounced for the IgG2a and IgG2b subclasses than for IgG1 and IgM, resulting in a shift of the ratio of immunoglobulin classes as a function of subcultivation of these tumor-derived cells.