Detection of keyhole limpet hemocyanin (KLH)-specific immune responses by intracellular cytokine assay in patients vaccinated with idiotype-KLH vaccine

Keyhole limpet hemocyanin (KLH) has been used as an immune potentiator to enhance antigen-specific responses against haptens and weak antigens including self-antigens. In the present study, we describe the optimization of the intracellular cytokine response to KLH in peripheral blood mononuclear cells (PBMC) of lymphoma and myeloma patients that were vaccinated with tumor-specific immunoglobulin (Id) conjugated to KLH. Addition of anti-CD28 antibody significantly enhanced cytokine-producing CD4⁺ T cells. While fresh PBMC showed maximal cytokine response 14 h after antigen stimulation, the frozen PBMC showed maximal cytokine responses by 24 h. Supplementation of the culture medium with fetal bovine serum gave a better signal-to-noise ratio than human AB serum in the intracellular detection of cytokines. The intracellular cytokine responses correlated with the cytokine measurements by enzyme-linked immunosorbent assay (ELISA). Together these results indicate that the intracellular cytokine assay is very helpful to measure antigen-specific immune responses, and in subsequent studies, we have utilized this sensitive technique to detect immune responses against tumor antigens such as idiotype.