These findings suggest both a genetic susceptibility and an environmental response in developing psoriasis. It is caused by the interaction between genetic susceptibility and environmental factors. Certain allele combinations appear to increase RHD autoimmune susceptibility. Some of the susceptibility genes may be population specific. NOD2 is a gene involved in Crohn's genetic susceptibility. This also affects essential granules present in immune cells leading to increased susceptibility to infection. Stress can result in immunosuppression, leading to an increased susceptibility to disease. There is also an increased susceptibility and severity of certain infections in pregnancy. In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea. There is a genetic element in individual susceptibility to cellulite. The original crossbreed was plagued by problems of low fertility, slow growth and disease susceptibility. Another advantage is the potential to predict antibiotic susceptibility of bacteria. The factors responsible for host susceptibility are not known. Exposure to residents is greatly dependent on individual susceptibility. There is evidence that susceptibility to PTSD is hereditary.