Antigen uptake: 1. Antigen can be recognized directly by IEL,
signals are sent to LT in the lamina propria. 2. When antigen is taken in by M cells using
transcytosis process, there are 2 possible mechanisms to stimulate the immune response: a)
antigen is directly taken in by macrophages or dendritic cells, which are able to process and
present to LT in the lamina propria, or b) antigen activates B cells, which stimulate LT in the
lamina propria. 3. Antigen uptake can be made by IEC using endocytosis process. The IEC
are able to act as APC and process the antigen, antigen is presented to LT in the lamina
propria. SIgA production: activated LT (LPL) produces cytokines, which stimulate LB
activation, and finally plasma cells, produce IgA. The IgA acquires the secretory component
on the IEC and is able to internalize into IEC; finally SIgA is available in the intestinal lumen
to exert surface protection. (Revolledo et al., 2006).