Human Immunity and Blood

The B is ABO type and + is an Rh type (Rh positive). While these are medically the most important blood type systems, similarly we all have many others that we could typed for as well.

The International Society of Blood Transfusion (ISBT) identifies about 30 major blood group systems, including the ABO and Rh systems.

Lymphoid stem cells derived from the bone marrow develop into competent T-lymphocytes with a functioning T-cell receptor and coreceptor in the thymus gland.

Factor XII is a protease involved in initiating the intrinsic blood clotting pathway when it binds to abnormal or negatively charged surfaces revealed by damage to endothelial cells of blood vessels.

Plasmin is in fact an active protease, which can break down the fibrin meshwork of the clot by dissolving the clot.

Immunoglobulins are produced by lymphocytes.

Thrombocytopenic purpura is characterized by excessive bleeding due to insufficient platelets. The term 'thrombocytopenic' literally means low platelet count, which prevents proper blood clotting and leads to spontaneous bruising and bleeding.

Haemoglobin consists of two components: heme (iron-containing porphyrin) and globin (protein). When iron is removed from haemoglobin, the remaining protein portion is called globin. This is distinct from bilirubin (a breakdown product) or haematin (an oxidized, iron-containing form).

Megakaryocytes are large, specialized cells in the bone marrow that produce platelets (thrombocytes) through fragmentation of their cytoplasm. They do not produce erythrocytes (from erythroblasts), granulocytes (from myeloblasts), or agranulocytes (from lymphoblasts).

Histamine is primarily stored and released by mast cells (found in connective tissue) and basophils (a type of granulocyte). Macrophages and Kupffer cells are phagocytic cells involved in antigen presentation and debris clearance, not histamine secretion.

Platelets (thrombocytes) are not true cells but small, anucleate cell fragments derived from megakaryocytes. Monocytes, neutrophils, and basophils are all complete, nucleated white blood cells (leukocytes).

Blood group A has A antigens on red blood cells and anti-B antibodies in plasma. The ABO system is based on the presence or absence of A and B antigens on RBC surfaces. Blood type A has only A antigens, type B has only B antigens, type AB has both, and type O has neither.

Agranulocytes are white blood cells lacking visible cytoplasmic granules, primarily lymphocytes and monocytes. In contrast, eosinophils, basophils, and neutrophils are granulocytes, each containing distinctive granules that give them their staining properties and functional characteristics.

Leucopenia is a condition characterized by decreased white blood cell (WBC) count/production. It's not uncontrolled WBC (A), uncontrolled RBC (B), or excess platelets (C). The term literally means 'white blood cell deficiency'.

Agglutinogens (A and B antigens) are glycoproteins on the surface of red blood cells (RBCs). They determine blood type. Serum (A) contains antibodies, plasma (C) is serum plus clotting factors, and hemoglobin (D) is inside RBCs - none carry agglutinogens.