NOD2 Variants and Antibody Response to Microbial Antigens in Crohn’s Disease Patients and Their Unaffected Relatives

Quartile analysis of the CD cohort for the 4 tested microbial antigens (ASCA, I2, OmpC, and CBir1). Reactivity to each antigen was divided into 4 quartiles and a value ascribed to a given individual based on their quartile of reactivity to each antigen (left panel). Quartile sums were calculated by the addition of the quartile value for each antigen (range, 4–16; see Materials and Methods). The distribution of quartile sums is shown (right panel). Values for binding levels are in ELISA units except for ASCA, which is presented in standardized format. Quartile sums were calculated similarly for unaffected relatives and healthy controls based on the distribution within each group (the quartile cutoff values and the distribution of quartile sums for the other 2 groups are not represented in this figure).

The frequency of carriage of any NOD2 variant increased with qualitative antibody reactivity, as represented by the antibody sum (number of positive antibodies; range, 0–4). The dotted line represents the 31.8% frequency of carriage of at least one NOD2 variant, across the entire cohort.

The frequency of carriage of any NOD2 variant increased with semiquantitative antibody reactivity, as represented by the quartile sum (range, 4–16). The dotted line represents the 31.8% frequency of carriage of at least one NOD2 variant, across the entire cohort.

The cumulative semiquantitative antibody reactivity, as represented by mean quartile sum, increased with increasing number of NOD2 variants by trend analysis (P = .002).

The cohort of patients with CD was divided into mutually exclusive groups based on all possible permutations of antibody positivity: no positive antibodies, single antibody positivity (4 groups in set 1), double antibody positivity (6 groups in set 2), triple antibody positivity (4 groups in set 3), and all antibodies positive. Within each of the 3 sets where the groups had the same number of antibody positivity, there was no statistically significant difference in the frequency of NOD2 variants among sets 1, 2, and 3, respectively.

The cumulative semiquantitative antibody reactivity in unaffected relatives of patients with CD, as represented by mean quartile sum, was higher in individuals carrying any NOD2 variant than in those carrying no variant (P = .02). *The quartile sum in unaffected relatives is based on quartiles of seroreactivity within this cohort specifically and is not representative of the same magnitude of reactivity as an equivalent quartile sum value in a patient with CD or a healthy control. No individuals carried 2 variants.

The cumulative semiquantitative antibody reactivity in healthy controls, as represented by mean quartile sum, was numerically higher (although not achieving statistical significance) in individuals carrying any NOD2 variant than in those carrying no variant (P = .07). *The quartile sum in healthy controls is based on quartiles of seroreactivity within this cohort specifically and is not representative of the same magnitude of reactivity as an equivalent quartile sum value in a patient with CD or unaffected relative. No individuals carried 2 variants.