Human Immunity and Blood

LFA-1 is a member of the integrin family, molecules concerned with leukocyte binding to endothelial cells and to extracellular matrix proteins. The VLA molecules are also members of the integrin superfamily.

The peptide in the MHC groove is derived from intracellular proteins, either endogenous or exogenously derived.

Cortical epithelial cells may be relatively inefficient antigen processors and only deliver a weak signal which induces proliferation rather than deletion of immature thymocytes.

Neutrophils are chemotactically attracted to the site of inflammation by C5a and mast cell chemotactic factors such as leukotriene B4.

Factor IX is known as the Christmas factor, named after the first patient diagnosed with the deficiency.

Human blood has two parts, fluid and cellular. The fluid part is known as blood plasma, that makes 55% of total blood volume, and the rest are the cellular components. When a sample of blood is centrifuged, results show separation of blood into different layers, based on their density. Three layers are visible after centrifugation is complete. The bottom layer is red colored that is composed of Red Blood Cells (RBCs), above it there's a white band, made up of White Blood Cells (WBCs) and platelets. The third or the topmost layer is a straw colored liquid, that is made up of blood plasma. The cells present in the blood, are also known as formed elements.

Part of the swelling, due to injury or infection, is caused by diapedesis. The white cells are intensely active because apart from destroying bacteria they also work to form a barrier around an infection that can help prevent the rest of the body from becoming infected. In small localized infections, this effect provided by diapedesis can be quite effective. In larger infections, the migrating infection may overpower the migrating white cells.

Blood plasma is the yellow liquid component of blood, in which the blood cells in whole blood, are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells). It is mostly water (93% by volume) and contains dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide.

The erythrocytes or RBC are the red cells of blood which constitute most of the cellular component of blood. A matured red blood cell cannot divide and the biconcave shape makes gas exchange quicker, due to less distance between center and periphery and and more surface area.The RBC contain hemoglobin, and most of the functions of RBC, like, gas transport, acid-base balance and formation of bilirubin, are due to presence of hemoglobin. RBC's are responsible for the major portion of the viscosity of blood. 

Monocytes are largest agranulocytes with kidney-shaped nucleus and plenty of cytoplasm. They are phagocytic in nature. They represent 3-8% of WBC

Lymphocytes are agranulocytes with round or kidney shaped nucleus and scanty cytoplasm. They are of three types, B-Lymphocytes, T-Lymphocytes and Natural killer cells. B-lymphocytes are stimulated by an antigen and form plasma cells. These plasma cells produce antibodies, which react with antigen, and inactivate them. Lymph mainly consists lymphocytes.

Basophils are granular leukocytes, containing basophilic granules, in the cytoplasm. The cell nucleus is S-shaped. Basophil releases heparin, which prevents clotting of blood and histamine, which causes tissue damage and allergy. They represent 0.5% of WBC

Eosinophils are granular leukocytes, containing acidophilic granules, in the cytoplasm. The nucleus is usually bi-lobed. The cells show amoeboid movement and phagocytic power. The histamine released by this cell helps in combating infection. They represent 2-4% of WBC

Neutrophil are granular leukocytes, containing neutral granules, in the cytoplasm. They represent 60-70%of WBC cells. The cell nucleus is 2-7 lobed. In the neutrophil of human female adjacent to the nucleus, a drumstick like hetero chromatin body is present, called Barr Body. It represents one of the two X chromosomes of female. The primary functions of neutrophil are phagocytosis, ingestion and digestion of invading microorganism.

Eosinophils are granular leukocytes, containing acidophilic granules, in the cytoplasm. The nucleus is usually bi-lobed. The cells show amoeboid movement and phagocytic power. The histamine released by this cell helps in combating infection. They represent 2-4% of WBC