(A) Early recognition of viruses via pattern recognition receptors such as intracellular DNA and RNA sensors by innate immune cells results in an interferon and cytokine response. Virus and viral antigen uptake by dendritic cells, macrophages, and epithelial M cells leads to activation of the adaptive immune system.
(B) Dendritic cells in the lamina propria migrate to the draining mesenteric lymph nodes and present viral antigens to virus-specific T cells.
(C) Activated T cells migrate to the intestinal tissue and elicit antiviral immunity by cytokine secretion or cytotoxic activity.
(D) B cells activated in Peyer’s patches undergo IgA class switching and differentiate into plasma cells with the help of follicular T helper cells. Intestinal plasma cells produce secretory IgA that can neutralize viruses in the mucosa.