In recent days, necrotizing enterocolitis is one of the most common and devastating problem in preterm infants. Therefore, it became a high growing research topic in the last decade.

The development of medical care increases the survival of preterm babies and consequently increase the number of cases with this serious problem. A systematic review shows the incidence of necrotizing enterocolitis is about 2-7% in babies less than 32weeks gestation and 5-22% in baby's birth weight less than 1000gram.

In 2011, study on average cost of necrotizing enterocolitis in United States shows average cost of health service for preterm baby without necrotizing enterocolitis and with necrotizing enterocolitis 74,004 $-198,040 $ respectively.Babies surviving from necrotizing enterocolitis are at risk of long term complication such as short bowel syndrome and intestinal stricture.Furthermore, impairment of neurodevelopment and growth are usually observed in these babies.In spite of decades of researches on the disease, pathogenesis of necrotizing enterocolitis still unclear. We still don't know how to prevent and treat the disease. However, advancement of researches in the field of microbiology and cellular biology of the intestine of preterm infants could lead to more understanding for early diagnosis, prevention and proper treatment. Enteral feeding in preterm pigs lead to upregulation of inflammatory and pattern recognition receptor genes including interleukin8 and Toll like receptor-4 with corresponding condensation of chromatin configuration that lead to initiation of inflammatory process and development of necrotizing enterocolitis. It is not known if these changes are present in human preterm bowel.T cell effector function in preterm infant immune response is characterised by preponderance of interleukin-8 producing T-cells and has the potential to activate neutrophils and γδ T cells.γδ T cells are predominant intra-epithelial lymphocyte in immature preterm gut and has a role in maintaining intestinal integrity.

Inclusion Criteria:

• Cases of necrotizing enterocolitis diagnosed by modified Bells criteria, radiological picture and need surgical intervention.

Exclusion Criteria:

• Cases of severe intrauterine growth retardation.
• Cases with severe congenital anomalies.

Surgical cases of necrotizing enterocolitis and control from babies with intestinal operations for non necrotizing enterocolitis pathology (preterm and term infants).