Regulation of Homocytotropic Antibody Formation in the Rat

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Abstract
An antigen-specific subcellular component, possibly from thymus derived (T) cells that regulate homocytotropic antibody (HTA) formation against dinitrophenylated Ascaris suum extract (DNP-As), was extracted from mechanically disrupted thymocytes and spleen cells of rats hyperimmunized with the homologous antigen. This cell free extract, when injected into HTA-producing animals that had been 400R x-irradiated and immunized with DNP-As and Bordetella pertusis vaccine so as to produce high and persistant HTA formation, exerted a strong inhibitory effect on the ongoing HTA production of the recipients. A similar thymocyte extract obtained from rats hyperimmunized with the carrier (Ascaris extract, As) alone also showed the inhibitory activity, whereas that from rats hyperimmunized with the hapten coupled to a different carrier (DNP-bovine serum albumin) or with Freund's complete adjuvant alone did not. The inhibitory activity of the thymocyte extract was completely abolished by absorption with immunoadsorbents composed of DNP-As or As, but not with that of DNP-BSA, indicating that the active component has an affinity to carrier molecules. However, the inhibitory activity was not absorbed with antisera directed to rat Fab, µ chain and polyvalent immunoglobulins, suggesting that the active component is not likely to be an immunoglobulin. The activity was significantly reduced by absorption with an immunoadsorbent composed of anti-rat thymocyte serum. These results suggest that the inhibitory cell interaction in the rat HTA formation, which has previously been reported by us, is mediated by this subcellular component of primed T cell which is not immunoglobulin in nature but has an affinity and specificity to the carrier molecule.

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