This is consistent with our observation of a higher frequency of infection in the BPD infants (Table 1), including sepsis and pneumonia (Additional file 1: Table S1), and also with an adaptive immune response as indicated by apparent shifts from naïve to memory among B cells, CD4 T cells and CD8 T cells (Additional file 1: Table S2). This evidence concerns the gene CD8A and susceptibility to pneumonia measurement.