No association of childhood ALL with KIR gene frequencies. (A) The frequency of 6 inhibitory KIR genes (KIR2DL1, 2DL2, 2DL3, 2DL5, 3DL1, 3DL2) and 6 stimulatory KIR genes (KIR2DS1, 2DS2, 2DS3, 2DS4, 2DS5, 3DS1) was analyzed in ALL patients. Our study population (0-18 years) consisted of 185 children with B-ALL (dark gray columns) and 33 children with T-ALL (light gray columns) of European origin. The ethnically matched control group (black columns) consisted of 204 unrelated randomly selected healthy volunteers. PCR-based KIR genotyping was performed as described by Vilches et al.³  As an additional quality control, 10% of samples were randomly selected and analysis repeated with an independent KIR typing protocol as described by Uhrberg et al.⁴  Similarly, all samples exhibiting rare KIR genotypes (frequency < 0.5%) were controlled in this way.⁴  Samples with discordant typing results (n = 9) were excluded from the analysis. (B) Distribution of group A and B KIR haplotypes according to previous definitions.⁵  Statistical significance was tested by 2-sided Student t test and 95% confidence intervals are indicated.