An Examination of the Development and Localization of Key Immune Cells in Developing Pouch Young of the Red‐Tailed Phascogale (Phascogale calura)

Abstract

Cells expressing the surface markers CD3, CD4, CD79b, IgM, MHC class II, and ModoUG (nonclassical MHC class I) were detected in red-tailed phascogale tissues using immunohistochemistry, and the appearance and localization of cells observed here was consistent with previous observations in other marsupial species. CD3 + cells were first detected at one day postpartum (dpp) in the thymus, followed by ModoUG + cells at 5-7 dpp in the thymus and lymph nodes. CD79b + cells were first detected at 12-14 dpp in bone marrow, spleen, and lymph nodes. IgM + cells were first detected at 12-14 dpp in thymus, bone marrow, spleen, and lymph nodes. MHC class II + cells were first detected at 12-14 dpp in thymus, bone marrow, and lymph nodes. CD4 + cells were detected in adult thymus and spleen only. The presence of the mature immune cell populations and their localization to characteristic T and B cell zones in mature lymphoid tissues with normal histological structure indicates that red-tailed phascogales develop immunocompetence by the end of pouch life.

Red‐tailed phascogales: A review of their biology and importance as model marsupial species

“…Much has already been investigated in terms of immune system development in the phascogale, including the development of the thymus, bone marrow, liver, spleen, lymph nodes, and some mucosal‐associated lymphatic tissues (Borthwick & Old, 2016; Borthwick et al, 2019), thus enabling more in‐depth studies in the future. The thymus is the first immune tissue to histologically mature in the red‐tailed phascogale, as it is in other marsupials (Basden et al, 1997; Old et al, 2003a).…”

“…Confirmation of cross‐reaction and localization of anti‐CD3ε and anti‐MHC II using immunohistochemistry were also described (Old et al, 2006). However, more recently Borthwick et al (2019) conducted a more comprehensive investigation using immunohistochemistry into the expression of a wider number of immune molecules (CD3ε, CD4, CD79b, MHC II, and ModoUG) in the developing immune tissues of the phascogale. CD3ε is a mature T‐cell marker for the CD3 protein complex involved in T‐cell activation (Kurucz et al, 1993), with the tammar wallaby ( Macropus eugenii ) the first marsupial to have it characterized (Old et al, 2001).…”

“…CD3ε is a mature T‐cell marker for the CD3 protein complex involved in T‐cell activation (Kurucz et al, 1993), with the tammar wallaby ( Macropus eugenii ) the first marsupial to have it characterized (Old et al, 2001). CD3 was initially detected in the phascogale thymus on Day 1 postpartum, while CD4 was only detected in adult thymus and spleen (Borthwick et al, 2019). The B‐cell marker CD79b (Reth, 1989) was first detected 12–14 days after birth in the bone marrow, spleen and lymph nodes, and IgM likewise first detected in these tissues and the thymus at this age (Borthwick et al, 2019).…”

“…CD3 was initially detected in the phascogale thymus on Day 1 postpartum, while CD4 was only detected in adult thymus and spleen (Borthwick et al, 2019). The B‐cell marker CD79b (Reth, 1989) was first detected 12–14 days after birth in the bone marrow, spleen and lymph nodes, and IgM likewise first detected in these tissues and the thymus at this age (Borthwick et al, 2019). MHC II was also first detected for the first time at Day 12–14 day after birth in the phascogale thymus, bone marrow, and lymph nodes (Borthwick et al, 2019).…”

“…The B‐cell marker CD79b (Reth, 1989) was first detected 12–14 days after birth in the bone marrow, spleen and lymph nodes, and IgM likewise first detected in these tissues and the thymus at this age (Borthwick et al, 2019). MHC II was also first detected for the first time at Day 12–14 day after birth in the phascogale thymus, bone marrow, and lymph nodes (Borthwick et al, 2019). ModoUG, a nonclassical MHC molecule (Gouin et al, 2006; Papenfuss et al, 2015) was first detected 5–7 days after birth in the thymus and lymph nodes (Borthwick et al, 2019).…”