GAPDH and necrotizing enterocolitis: Mucosal mRNA expression levels of CD45 and CD4 were significantly decreased in A-NEC-XBP1s patients compared with A-NEC-XBP1u patients when normalized to GAPDH (Figure 4A and 4B), suggesting that overall there were less hematopoietic cells and CD4+ T cells in A-NEC-XBP1s patients.