A Histological Investigation of the Lymphoid and Immunohaematopoietic Tissues of the Adult Stripe-Faced Dunnart <i>(Sminthopsis macroura)</i>

Abstract

This is the first published description of the lymphoid and immunohaematopoietic tissues of an Australian polyprotodont, the stripe-faced dunnart, Sminthopsis macroura and the first account of bronchus-associated lymphoid tissue (BALT) in a metatherian. Histologically, the tissue beds are similar in appearance to those reported in other adult eutherian and metatherian mammals. The liver and bone marrow were mature and virtually no haematopoietic activity was observed. The thymus had undergone involution but retained some lymphocytes. The spleen was similar to that observed in other metatherians containing areas of red and white pulp separated by a marginal zone. Lymph nodes, except for a pair in the posterior abdomen, were difficult to locate but were similar to those observed previously in other adult metatherians. Peyer’s patches were present; however, they lacked dome regions and sometimes had villi above them. BALT appeared to be both compartmentalised and non-compartmentalised in the adult stripe-faced dunnart.

Development of Lymphoid Tissues of the Stripe-Faced Dunnart <i>(Sminthopsis macroura)</i>

“…The appearance of the intestines was similar to that described for other marsupials [van Lennep, 1962;Deane, 2001, 2002;Old et al, 2003]. There was no caecum or appendix present and this lack of a caecum and appendix is similar to that observed in Antechinus species [Poskitt et al, 1984c].…”

“…The youngest age at which lymph nodes were observed was 31 days. It was histologically mature in appearance and similar to those observed in adult stripe-faced dunnarts [Old et al, 2003] as well as those of other adult marsupials [Block, 1964;. A summary of lymph node development in marsupials is shown in table 2.…”

“…This may suggest that BALT is only present in adult dunnarts, as described previously [Old et al, 2003] or only after microbial invasion of the lungs as observed in humans and cats [Pabst and Gehrke, 1990]. The presence of BALT in the dunnart is most likely to be dependent on the antigenic load in the lungs [Sminia et al, 1989].…”

“…Yadav [1973] documented the structure of the thoracic thymus in 21 species of dasyurids, whilst Poskitt et al [1984a] studied the involution of the thymus, spleen, Peyer's patches and lymph nodes in the brown antechinus (Antechinus stuartii) and the Australian dusky antechinus (Antechinus swainsonii). Most recently, Haynes [1991] described the cervical lymph nodes of the adult fat-tailed dunnart (Sminthopsis crassicaudata) and the stripe-faced dunnart as having an unusual pigmentation and presence of mast cells, whilst Old et al [2003] described the immune tissues in the adult stripe-faced dunnart. However, little has been done to examine the development of the lymphoid tissues of this group of small, unique marsupials.…”

The appearance and distribution of mature T and B cells in the developing immune tissues of the stripe‐faced dunnart (Sminthopsis macroura)

“…Although little is known about this marsupial in the wild (Cronin, 1996), observations of captive populations have confirmed that it is nocturnal and feeds on invertebrate prey (Godfrey, 1969). Captive populations of this animal have been used in studies of developmental biology (Selwood & Woolley, 1991; Selwood & Hickford, 1999) and, more recently, immunology (Old et al. 2003a,b, 2004).…”