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T H 1 cells play an important role in classical macrophage activation as part of type 1 immune response against intracellular pathogens (such as intracellular bacteria) that can survive and replicate inside host cells, especially those pathogens that replicate even after being phagocytosed by macrophages. [45]
Monocytes are produced by the bone marrow from precursors called monoblasts, bipotent cells that differentiated from hematopoietic stem cells. [5] Monocytes circulate in the bloodstream for about one to three days and then typically migrate into tissues throughout the body where they differentiate into macrophages and dendritic cells.
A human pathogen is a pathogen (microbe or microorganism such as a virus, bacterium, prion, or fungus) that causes disease in humans.. The human physiological defense against common pathogens (such as Pneumocystis) is mainly the responsibility of the immune system with help by some of the body's normal microbiota.
The following outline is provided as an overview of and topical guide to concepts related to infectious diseases in humans.. Infection – transmission, entry/invasion after evading/overcoming defense, establishment, and replication of disease-causing microscopic organisms (pathogens) inside a host organism, and the reaction of host tissues to them and to the toxins they produce.
In general, phagocytes patrol the body searching for pathogens, but are also able to react to a group of highly specialized molecular signals produced by other cells, called cytokines. The phagocytic cells of the immune system include macrophages, neutrophils , and dendritic cells.
All white blood cells are produced and derived from multipotent cells in the bone marrow known as hematopoietic stem cells. [3] Leukocytes are found throughout the body, including the blood and lymphatic system. [4] All white blood cells have nuclei, which distinguishes them from the other blood cells, the anucleated red blood cells (RBCs) and ...
Mast cells have Toll-like receptors and interact with dendritic cells, B cells, and T cells to help mediate adaptive immune functions. [93] Mast cells express MHC class II molecules and can participate in antigen presentation; however, the mast cell's role in antigen presentation is not very well understood. [ 94 ]
Special forms of B cell called plasma cells produce antibodies; little versions of the specialized B cells, called memory B cells, remain stored in lymph glands prepared for the next invasion by the foreigner. Although the products of B cells, the antibodies, stick onto their target invader, they most often do not kill the invader.