Human Immunity and Blood

White blood cells are phagocytic in nature. They engulf germs entering the body.

Blood consists of a fluid called plasma, which has red blood corpuscles (RBC), white blood corpuscles (WBC) and blood platelets. Blood circulates throughout the body in blood vessels. The blood transports oxygen, nutrients, hormones to tissues and organs. Lymph is a straw coloured fluid similar to blood but does not have RBCs. Lymph flows in special vessels called lymph vessels. Its function is to form a defence system for the body .

Rouleaux formation is the stacking of red blood cells (erythrocytes) like a pile of coins, which occurs due to the discoid shape of RBCs and increased plasma proteins (especially fibrinogen). This is distinct from agglutination (antibody-mediated clumping) and coagulation (clot formation). Rouleaux formation is a normal phenomenon that aids RBC transport through capillaries.

Sodium oxalate prevents blood clotting by binding calcium ions, which are essential cofactors in the coagulation cascade. By removing calcium, the anticoagulant disrupts the clotting process and keeps blood in liquid form for storage.

Basophils are granulocytes that release histamine and heparin during allergic responses but do not phagocytose pathogens. In contrast, neutrophils and eosinophils (acidophils) are actively phagocytic cells that engulf and destroy microorganisms.

Leukaemia (leukemia) is a cancer of white blood cells, causing overproduction of abnormal WBCs that crowd out normal blood cells. Anaemia involves red blood cell deficiency. Jaundice is liver-related. Haemophilia is a clotting disorder. The question asks specifically about WBCs.

Blood group O is characterized by the absence of both A and B antigens on the surface of red blood cells. However, individuals with type O blood possess both anti-A and anti-B antibodies in their plasma. This makes type O the universal donor for red blood cells, as their cells can be transfused to recipients of any ABO type without triggering an immune response.

The Rh (Rhesus) factor was first discovered in the blood of Rhesus monkeys, which is why it bears this name. This blood group system is crucial in transfusion medicine and pregnancy, as Rh incompatibility can cause hemolytic disease in newborns.

When incompatible blood types mix, antibodies in the plasma bind to antigens on red blood cells, causing agglutination (clumping). This antigen-antibody reaction can trigger serious transfusion reactions.

Histamine and heparin are two compounds produced by mast cells.

One of the examples of gut-associated lymphatic tissues is tonsils.

The process of formation of blood corpuscles is known as haemopoiesis.

The substance which is found in most cells and is involved in allergic and inflammatory reaction is histamine. Histamine is amine formed from histidine that stimulates gastric secretions and dilates blood vessels; released by the human immune system during allergic reactions.

The connective tissue cells that synthesise antibodies are known as plasma cells.

It is correct the principle of clonal selection, and analog of natural selection, is implemented by the immune system.