Expression of λ1 and κ light chains, 6-19 Id, and anti-IgG2a RF activities in L8D, 6-19J, and 6-19 IgG3 mAbs and expression of 6-19 κ, J558 λ1, and 6-19 γ3 mRNA in 6-19, L8D, and 6-19J cells.

(A) For the detection of IgG3 bearing λ1, κ, or 6-19 Id, purified L8D (■), 6-19J (▨), and 6-19 (▪) mAb (10 μg/mL) were added to microtiter wells coated with rat antimouse γ3 mAb. Assays were developed with anti-λ1, anti-κ, or anti–6-19 Id mAb conjugated with alkaline phosphatase, as described previously.11 Anti-IgG2a RF activities were determined by ELISA as described.8 Results are expressed as OD at 405 nm. (B) The presence of κ-, λ1-, and γ3-specific mRNA was examined by amplifying cDNA made from the cultured cell lines with 6-19 κ, J558 λ1, and 6-19 γ3-specific primers. Polymerase chain reaction (PCR) products were visualized after electrophoresis through 2% agarose gels by staining with ethidium bromide. Lane 1, 6-19; lane 2, L8D; lane 3, 6-19J; lane 4, PCR mix without cDNA. M, molecular weight marker (DNA molecular weight marker VI; Boehringer Mannheim).