The Green turtle possesses most of the immunologic capabilities of mammals. Yet the gross distribution and anatomical structure of the components of the immune system have not been described for Chelonia mydas. Fresh tissue collected from 3-4 year old cultured turtles were examined for grossly evident lymphoid structures, Hidden structures were unmasked by overnight treatment with 10% acetic acid at 4°C. Standard histological stains were employed to describe the morphology of the various structures.

Chelonia mydas possesses a well developed spleen and thymus. The papillae of the oral cavity resemble the lingual tonsils of min. Focal accumulations of lymphoid cells were more prominent on the lateral and ventral surfaces of the larynx and trachea, an area where inhaled particulates are most likely to lodge. The digestive tract contained numerous aggregates throughout the tract, with the structures becoming more prominent in the posterior segment of each compartment. The urinary bladder and cloaca were heavily invested with aggregates of cells. The absence of lymph nodes and prominence of lymphoid aggregates at the mucosal level indicate that these structures are important in trapping and processing antigens for immune responses. This also enhances the likelihood that the spleen is the major antibody forming organ in the turtle, as has been suggested for other reptile classes.