The image shows a confocal microscope image of immune cells in the epithelial lining of the intestine of a young mouse. The cells are localised within specialised lymphoid tissue in the epithelial lining of the intestine called a Peyer's patch. Here, B and T cells interact to mediate an effective antibody response against the gut microbiota. Naïve B cells are shown in orange, while proliferating cells - including germinal centre B cells - are blue. All T cells are stained green and regulatory Foxp3+ T cells can be recognised by their purple centre.