Measurement of murine IgG and IgM concentrations in the SCLC MAb panel; effects of concentration on sensitivity and specificity.

Sensitive, solid-phase enzyme immunoassays for detecting murine IgM and IgG were developed and used to quantitate immunoglobulin concentrations in the SCLC MAb panel. Among the IgM MAbs, most contained between 10-75 micrograms ml-1. At least three IgM MAbs, however, contained less than 2 micrograms ml-1 and six contained greater than 75 micrograms ml-1. Two of the three IgM's containing less than 2 micrograms ml-1 immunoglobulin were found to cluster with the negative controls. Among the IgG MAbs, the majority contained between 10-100 micrograms ml-1 Ig. At least five of the IgG MAbs contained greater than 100 micrograms ml-1; and six were less than 2 micrograms ml-1. Three of the MAbs containing less than 2 micrograms ml-1 IgG clustered with the negative controls. Many of the panel members containing greater than 50 micrograms ml-1 antibody were found to give nonspecific immunostaining on tissues and cell lines. Often this nonspecific immunostaining was eliminated when these MAbs were diluted. Although only a minority of the panel members contained very high or very low concentrations of antibody, the data highlight the inherent difficulties that may result, in part from this variable and suggest that efforts be made to normalise the Ig concentrations of panel members in future workshop panels.