Evidence for correlation between the antigenic specificity and charge of human IgG. A study of antibody-inducing lymphocyte mediated cell damage

Abstract

This study has investigated the charge of IgG involved in antibody dependent lysis of cells by lymphocytes. The following conclusions are drawn:

1. That under certain conditions the physical alteration of IgG can result in molecules which compete with antibody bound to target cell antigens for receptors on cytotoxic lymphocytes. This phenomenon is used in a cytotoxicity inhibition test to determine the charge distribution of antibodies, which are capable of interacting with cytotoxic lymphocytes. This test is independent of the antigenic specificity of the inhibiting antibody.

2. The charge distribution of rat antibodies capable of reacting with cytotoxic lymphocytes, as assessed by cytotoxicity inhibition is similar to that of specific rat antibody capable of inducing cytotoxic activity against a xenogeneic target cell. By both criteria the isoelectric points ranged between pH 5 and 10.

3. Spontaneously occurring human antibody against a human line of target cells was found to have a highly restricted range of isoelectric points separating between pH 8 and 9.5. On the other hand assay of these sera by cytotoxicity inhibition showed a normal distribution of total antibody capable of reacting with cytotoxic lymphocytes.

It is suggested that a likely explanation of these findings is that the human antibody with specificity for an allogeneic strain of target cells is cross reacting with a single antigen on the target cells and that the antibody from specifically immunized rats is likely to be against multiple antigens.