A Novel Methodology for Quantitating the Enhancement of Cutaneous Delayed-Type Hypersensitivity by IMREG-1: A Measure of the Immunopotentiation of Cell-Mediated Immunity

IMREG-1, a low-molecular-weight immunomodulator derived from normal human leukocyte dialysates, has been shown to enhance cutaneous delayed-type hypersensitivity (DTH) responses to recall antigens. Both IMREG-I and the biologically active peptides (Tyr-Gly[YG] and Tyr-Gly-Gly[YGG]) identified therein are able to accelerate and enhance DTH in a concentration-dependent manner. In this study, we describe a novel methodology for analyzing and quantitating this response and demonstrate its use with data comparing drug to placebo. Subjects demonstrating prior sensitivity to a recall antigen (tetanus toxoid) received intradermal injections of tetanus toxoid alone (control) and either dilutions of IMREG-1 plus antigen, or placebo plus antigen, on the volar surface of the forearm. The response, as measured by area of erythema, was calculated and plotted as a function of time. The area under the resulting curve (AUC) was then determined by use of the trapezoidal rule, whereby the area of a trapezoid formed between each sequential pair of time points was calculated. The AUC computed for each site receiving a dilution of IMREG-1 or placebo (test) was compared with the AUC computed at the site that received antigen alone (control) by means of a test to control (T/C) ratio. The respective T/C ratios for designated dilutions of IMREG-1 or placebo provided a basis of comparison between responses to IMREG-1 and to placebo, while also controlling for individual sensitivity in response to antigen. We demonstrate in this study that the enhanced response to IMREG-1 plus antigen is statistically different from that seen with placebo plus antigen. This response, as a function to time, predominantly appears in the 12- to 24-hr period after injection, illustrating the ability of the immunomodulator to accelerate, enhance, and sustain a DTH response. We further conclude that the effect of IMREG-1 in this context is one of immunopotentiation of cell-mediated immunity.