Immunohistochemistry of the lymphoid tissues of the tammar wallaby, Macropus eugenii

Abstract

The lymphoid tissues of the metatherian mammal, the adult tammar wallaby, Macropus eugenii, were investigated using immunohistochemical techniques. Five cross-reactive antibodies previously shown to recognize surface markers in marsupial tissues and five previously untested antibodies were used. The distribution of T-cells in the tissue beds of spleen, lymph node, thymus, gut-associated lymphoid tissue (GALT) and bronchus-associated lymphoid tissue (BALT) was documented using antibodies to CD3 and CD5. Similarly, B-cells were identified in the same tissues using anti-CD79b. Antibodies to CD8, CD31, CD79a and CD68 failed to recognize cells in these tissue beds. In general the pattern of cellular distribution identified using these antibodies was similar to that observed in other marsupial and eutherian lymphoid tissues. This study provides further information on the commonality of lymphoid tissue structure in the two major groups of extant mammals, metatherians and eutherians.

Fig. 1. Adult tammar wallaby cervical thymus stained with polyclonal anti-CD3, showing lymphocyte islands surrounded by large amounts of connective tissue and adipose (A). Most cells are CD3⁺ T-cells (arrows). Some lymphocyte-like cells were not stained by anti-CD3. ×400.

Fig. 2. Thoracic thymus of the adult tammar wallaby stained with anti-TCRα. Large numbers of stained TCRα⁺ cells (arrow) are seen. ×100.

Fig. 3. Spleen of the tammar wallaby stained with anti-CD5 antibodies. Lymphocytes are stained heavily in the T-cell areas (arrow). The pattern of staining is similar in distribution to that observed using anti-CD3 (data not shown). The mantle (Mn) and germinal centre (GC) are also lightly stained. ×100.

Fig. 4. Spleen of the tammar wallaby stained with anti-CD79b antibodies. Large numbers of lymphocytes are stained in the primary follicles (PF) and mantles of secondary follicles (arrow). Positive staining cells are also present throughout the red pulp (RP) areas. The peri-arterial lymphatic areas (PALS) are unstained. ×100.

Fig. 5. Spleen of the tammar wallaby stained with anti-TCRα antibodies. TCRα⁺ cells (arrow) are apparent in the T-cell areas. ×100.

Fig. 6. Lymph node of the tammar wallaby stained with anti-CD3 antibody. CD3⁺ stained lymphocytes are present throughout the paracortical areas (C). Some cells are also stained in the medulla (M) although much fewer in number. The majority of cells in the germinal centres (GC) are unstained. ×40.

Fig. 7. Lymph node of the tammar wallaby stained with anti-CD79b antibody. CD79b⁺ stained lymphocytes are present in the medulla (M) and the mantle (Mn) regions of lymph nodes. ×100.

Fig. 8. Adult tammar wallaby GALT showing CD3-positive T-cells (arrow) amongst the villi (V), present in large numbers. The lumen (L) can also be clearly observed. ×100.

Fig. 9. Gut-associated lymphoid tissue of the tammar wallaby stained with anti-CD5 antibodies. CD5⁺ stained cells are not as prevalent as those observed in the previous figure stained with anti-CD3. However, there are some cells stained in the villi (V) of the intestine. A few areas seem to have small accumulations of CD5⁺ cells (arrows). No cells stained within the lacteals of the villi. The lumen (L) is clearly identifiable. ×100.