Deviation from the product rule differs for the 3 types of repertoires and defines their conditional probabilities for KIR acquisition. (A) Deviations from the product rule for NK cells expressing 2, 3, and 4 KIRs are shown for the 3 distinct repertoires defined by their high-, intermediate-, and low-KIR expression frequencies. k-values were derived from the slope of the linear regression of observed data relative to a perfect fit to the product rule. (B) The conditional probabilities (shown in Table 1) for acquiring the nth KIR were given by Bayes rule (see “Calculation of conditional probabilities” for details). The conditional probabilities were then run in an algorithm for random and dependent KIR acquisition and the corresponding repertoires are shown.