Lymphoid Tissues

The human and mouse diverged over 50 million years ago; however, the major components of the lymphoid tissues are almost identical. The primary or central lymphoid organs include the bone marrow and thymus where B cells and T cells are generated, respectively. The secondary or peripheral lymphoid organs include the lymph nodes (LN), spleen, and lymphoid tissues associated with mucosa where B cells and T cells are activated to generate the adaptive immune response. Although the overall structure of the LNs are similar between humans and mice, humans have significantly larger numbers of LNs than the mouse (Haley, 2003). This is most likely due to the fact that a human is physically larger than a mouse; therefore more LNs are required in the human. In contrast to LNs, the mouse spleen has some anatomical and structural differences when compared to the human spleen. For example, the periarteriolar lymphocyte sheath and the marginal zone can be found only in the rodent (Sternberg, 1997), and the endothelial cells in human spleen that surrounds the vascular sinuses are missing in the mouse (Haley, 2003). A major difference between the human and mouse spleen is that mouse spleen has hema-topoietic activity, whereas the healthy human spleen does not (Cotterell et al., 2000). However it should be kept in mind that the mouse spleen is not the main source of hematopoiesis. The rat, on the other hand, has a much lower amount of hematopoietic activity in the spleen than the mouse, and thus more closely models the human spleen (Fujitani et al., 2004). The rodent and human also differ significantly in the bronchus-associated lymphoid tissue (BALT), which is not discernible in humans but is readily identifiable in the mouse and rat (Pabst and Gehrke, 1990). Peripheral blood immune cell composition also differs between humans and mice. Human blood contains more neutrophils (50-70%) than lymphocytes (20-40%), whereas mouse blood has a higher percentage of lymphocytes (50-70%) relative to neutrophils (15-20%) (Pabst and Gehrke, 1990).

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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