Selective decrease of serum immunoglobulin G1 as a marker of malignant transformation in colorectal tissue

Malignant diseases of various origins were previously shown to be associated with a characteristic and highly significant change in the serum pattern of immunoglobulin (Ig)G subclasses, comprised of a decrease in %IgG1 and an increase in %IgG2 relative to and independent of the absolute concentration of total IgG. The goal of the current study was to evaluate this phenomenon as an indirect marker in the primary diagnosis of colorectal carcinoma.

Using affinity chromatography, IgG1, IgG2, and total IgG were determined in 36 patients with colorectal carcinoma of different stages and compared with 162 apparently healthy controls.

It was found that: 1) the mean values for %IgG1 and %IgG2 of all carcinoma patients differed significantly from those of the controls; 2) no quantitative association was found with tumor stages, and four of five patients with incipient adenocarcinoma within a polyp exhibited the characteristic shift in IgG subclasses; 3) based on a calculated cutoff, the specificity and sensitivity of %IgG1 to discriminate between controls and carcinoma patients was found to be 88% and 74%, respectively; and 4) a quantitative correlation between individual %IgG1 values and the probability of correct assignment to carcinoma patients or controls was established.

The significant decrease in %IgG1 accompanied by an increase in %IgG2 in total serum IgG represents an indirect, tissue nonspecific, and early marker of malignant proliferation that distinguishes colorectal carcinoma patients from healthy controls with a specificity of 88% and sensitivity of 74%.