Bio AS: immunity

• What are the types of stem cells in bone marrow?

  Myeloid stem cells and Lymphoid stem cells
• What are the types of phagocytes?

  Neutrophils and Monocytes. Phagocytes are myeloid stem cells.
• What are neutrophils?

  neutrophils have granular cytoplasm, lobed irregular shaped nucleus, and many lysosomes and are found in the blood and tissue. Monocytes are immature cells that are found in the blood examples are macrophages, which mature in secondary lymphoid tissues such as the spleen or lymph nodes. They initiate a specific immune response.
• Examples of lymphocytes.

  we have two the B and the T. The T lymphocytes mature in the thymus gland and are involved in cell mediated immunity. Examples of T lymphocytes are three:

  1. T-helper cells: Secrete cytokines which act as a cell signaling molecule which activates the B-cells macrophages and T-cytotoxic cells.
  2. T-killer cells: Secrete perforin, destroy infected body cells and destroy non-self cells.
  3. T-suppressor cells: suppress or switch off immune response on recovery.
  4. Now we talk about the B cells which have two types:
• The B cells

  They are the plasma cell and memory cell.

  The plasma cell is short lived activated B lymphocytes, that make and release antibodies into the blood and the lymph.

  The memory cell lives many years and remains dormant until stimulated to produce plasma cells by the relevant antigen.
• What are phagocytes

  They are a type of white blood cells produced continuously by the bone marrow where they are Stored (In the bone marrow) and distributed around the body in blood. They undergo phagocytosis, which is the process by which large particles are taken up by cells, in the form of a vacuole thus removing any dead cells as well as any invasive microorganisms. Phagocytosis is a type of non-specific defense to a disease (phagocytes are involved in the non-specific immune response which is a faster response)
• What are neutrophils?

  Neutrophils are white blood cells that make up 60% of all white blood cells in the blood and the tissue.

  They are smaller in size and short lived, in which they die after killing and digesting the pathogens, where the dead neutrophils will collect at the site of infection forming pus.

  They are produced and matured from the myeloid stem cell in the bone marrow then released into the blood where they enter the tissues by squeezing through the holes in the capillary endothelium walls.
• What are macrophages?

  Macrophages are smaller in number than neutrophils they are larger in size than neutrophils and long lived. They are produced from the myeloid stem cells in the bone marrow, then released into the blood as monocytes then develop into macrophages once they leave the blood and settle in organs such as the spleen the lungs the liver, kidney, and lymph nodes.
• What is chemotaxis?

  its when the phagocytes are attracted to the chemicals released by the bacteria.
• The process of phagocytosis by neutrophil:

  Firstly, the bacteria releases a chemical that attracts the phagocytes, then the phagocyte will recognize the non-self antigen on the pathogen, then it will bind with the pathogen‘s antigen by its cell surface receptors and the bacterium/ pathogen will adhere directly to the neutrophil membrane, then the phagocyte cell surface membrane will infold around the bacteria to engulf it forming a phagosome.
• What are the B lymphocytes?

  1)They basically originate from the bone marrow in the lymphoid stem cell. They mature in the bone marrow then spread and concentration in the blood and the lymph tissue.

  2)They are involved in the humoral immune response(also called the antibody mediated immunity).

  3)They are smaller than phagocytes and have a large nucleus.

  4)They differentiate into plasma cells that produce and secrete antibodies. And produce memory B cells that live long and remain dormant until stimulated to produce plasma cells by the relevant antigen.
• What are the T lymphocytes?

  1)They originate from the bone marrow in the lymphoid stem cells, then they mature in the thymus gland.

  2) They spread and concentrate in the lymphoid tissue.

  3) They are smaller than phagocytes and have a large nucleus.

  4) They are cells that have the potential to either secrete cytokines( which act as a cell signaling molecule that activate the B cells macrophages and T-cytotoxic cells) or to kill infected cells. But they don’t release antibodies.
• What is a non-self antigen?

  it’s a substance that is recognized as foreign by the immune system and stimulates an immune response.
• What is a self antigen?

  It’s a substance produced by the body that the immune system doesn’t recognize as foreign and so they don’t stimulate an immune response, usually antigens are macromolecules made from proteins/ glycoproteins with specific sequence of amino acids.
• Two types of immune responses when a non-self antigen is recognized. what’s the non-specific immune response?

  The non-specific Immune response is faster:

  1. The pathogens will enter the body and cause inflammation which releases histamine, which stimulates the vasodilation in the blood vessels increasing the blood flow to infected areas, the capillary becomes more leaky so phagocytes will move out of the capillary endothelium pores to infected areas.
  2. Phagocytosis: You know the steps firstly chemostasis then recognition then attachment and endocytosis and digest and kill.