Blood is the liquid connective tissue consisting of plasma and cellular components (red blood cells, white blood cells, platelets) that transports oxygen, nutrients, hormones, immune cells, and waste products throughout the body. In cPNI, blood is also recognized as a reservoir for immune cells, cytokines, and potential pathogen-derived molecules.
Blood circulates through the cardiovascular system, with cellular components produced in bone marrow. During infection or inflammation, immune cells (particularly CD11b+ myeloid cells, TSH-producing leukocytes) migrate from spleen, lymph nodes, bone marrow, and blood to sites of tissue damage or infection. Blood also carries splice variant TSHβ produced by leukocytes, which can reach the thyroid gland during immune activation. Iron from degraded red blood cells is highly oxidative and toxic when released into tissues.
Blood serves as a 'highway' for immune cell trafficking during inflammation and infection. In chronic illness, blood can harbor low levels of pathogen-derived molecules (endotoxemia) or carry pro-inflammatory cytokines that signal to distant tissues. Haematomas (blood in tissue spaces) create oxidative stress from iron and physical barriers to healing. Understanding blood as an immune compartment helps explain systemic inflammation and tissue-level immune responses.
- Contains TSH-producing leukocytes even in non-infected state
- CD11b+ myeloid cells migrate from blood to thyroid during infection
- Spleen, lymph nodes, and blood contain leukocytes secreting low levels of TSHβ variant
- In chronic infection, blood carries HIGH levels of splice variant TSHβ
- Haematomas contain iron from degraded red blood cells, creating oxidative stress
- Blood-borne cytokines can signal to brain via circumventricular organs
- Clotted blood in tissue creates physical barrier to immune cell navigation
- Blood is a major reservoir of circulating immune cells during inflammation
- spleen — major reservoir of leukocytes that can be mobilized into blood during infection
- lymph nodes — contain TSH-producing leukocytes that traffic through blood
- bone marrow — produces blood cells including immune cells that enter circulation
- CD11b+ — myeloid lineage markers on blood-borne macrophages and monocytes
- TSHβ variant — splice variant TSHβ produced by leukocytes in blood, especially during chronic infection
- thyroid gland — receives immune cells and TSHβ variant from blood during infection
- iron — released from degraded blood cells in haematomas, creating oxidative stress
- red blood cells — oxygen carriers; their degradation releases toxic iron in tissue spaces
- leukocytes — white blood cells that traffic through blood to reach infection/inflammation sites
- Macrophages — monocytes in blood differentiate into tissue macrophages at sites of inflammation
- haematoma — blood in tissue space creates oxidative burden and physical barrier to healing
- endotoxemia — blood carries LPS from gut barrier dysfunction to cause systemic inflammation
- cytokines — blood transports cytokines that signal systemically during inflammation
- immune cell trafficking — blood is primary route for immune cell migration to tissues
- inflammation — blood delivers immune cells and mediators to inflamed tissues
- Oxidative Stress — iron from blood in tissues generates reactive oxygen species
- immune system — blood is a mobile compartment of the immune system
- circulation — blood flow determines oxygen and immune cell delivery to tissues
- platelets — blood clotting cells that also release inflammatory mediators
- ferritin — blood ferritin reflects iron storage and inflammatory status