CD28 and Crohn disease: A causal association was determined between 4 immune characteristics and Crohn disease after adjustment for FDR (PFDR < 0.05), namely: the percentage of IgD− CD27− B cells in lymphocytes, CD28 on CD39+ secreting CD4 regulatory T (Treg) cells, the percentage of human leukocyte antigen (HLA) DR+ CD4+ T cells in lymphocytes, and the percentage of naïve CD4+ T cells in all CD4+ T cells.