Development of lymphoid tissues of the stripe-faced dunnart (Sminthopsis macroura)

The development of the lymphoid tissues of a model marsupial, the stripe-faced dunnart, has been described from birth to weaning, a period of 2.5 months. At birth the lymphoid tissues, including the thymus, lymph nodes and mucosa-associated lymphoid tissues, were undeveloped. A thoracic thymus consisting primarily of stromal tissue was observed by day 4 after birth but by day 12, lymphocytes were observed in the thymus and some cortico-medullary differentiation was apparent. Lymph nodes were histologically mature by day 31, the earliest day investigated for this tissue. In gut tissue, lymphoid follicles were first observed by day 57 post-partum. No bronchus-associated lymphoid tissue was observed in any lung samples. The thymus, lymph nodes and gut-associated lymphoid tissues were all distinguishable before weaning (day 70) but not all were histologically mature. The sequence of development of the lymphoid tissues in the stripe-faced dunnart was similar to those observed in other marsupial species.