About 20% of cases of Crohn's disease appear to run in families. It is a "complex trait," which means that several genes at different locations in the genome may contribute to the disease. A susceptibility locus for the disease was recently mapped to chromosome 16. Candidate genes found in this region include several involved in the inflamatory response, including: CD19, involved in B-lymphocyte function; sialophorin, involved in leukocyte adhesion; the CD11 integrin cluster, involved in microbacterial cell adhesion; and the interleukin-4 receptor, which is interesting, as IL-4-mediated functions are altered in IBDs.