Terms for Immune System & Blood

 

Immune System:

 

B cells: produce antibodies, which bind to foreign antigens* & aid in their destruction

-       antibodies may bind to free antigens & antigens on the cell surface of invading cells such as bacteria

-       component of humoral immunity

-       produced in bone marrow; mature in bone marrow

 

T cells: 2 major classes:

-       cytotoxic T cells: bind to & destroy body cells expressing foreign antigens (virus-infected cells & cancer cells)

-       helper T cells: stimulate B cells to make antibodies & aid in activation of cytotoxic T cells

-       component of cell-mediated immunity

-       produced in bone marrow; mature in thymus

 

* antigens are molecules that elicit an immune response

 

Phagocytosis:

phagosomes, lysosomes & phagolysosomes are all parts of a phagocyte that are involved in the breakdown (digestion) of bacteria & cellular debris...

 

phagocyte: an immune system cell that breaks down & destroys bacteria & cellular debris

 

phagosomes: vesicles (membrane-enclosed sacs in a cell) that are formed when the plasma membrane of a phagocyte engulfs a bacterial cell or large particle & pulls it inside the cell (the bacterial cell or particle is then trapped in the phagosome)

 

lysosomes: vesicles in the cell that carry digestive enzymes that break down worn out cellular components into their subunits

 

phagolysosomes: when a phagosome fuses with a lysosome, the resulting vesicle is called a phagolysosome... the enzymes from the lysosome are used to destroy the bacterial cell or particle in the phagosome)

 

Blood:

 

Formed elements in blood: Erythrocytes (red blood cells), Leukocytes (white blood cells), Platelets

 

Granulocytes: Neutrophils, Eosinophils, Basophils

Agranulocytes: Lymphocytes, Monocytes

 

Leukocytes in order of decreasing abundance in blood:

Neutrophil, Lymphocyte, Monocyte, Eosinophil, Basophil

 

Albumin: plasma protein involved in transport of small molecules (calcium, fatty acids, thyroid hormone, etc.) & maintaining osmotic pressure in blood

 

Immunoglobulins (antibodies): help to fight infection by binding to & destroying bacteria & foreign antigens

 

Fibrinogen & Prothrombin are proteins involved in blood clotting:

-       Fibrinogen: precursor to fibrin, which helps to bind platelets together to form a blood clot (to help in healing a damaged blood vessel)

-       Prothrombin: precursor to thrombin, which activates fibrin

 

Plasma: fluid component of blood

Serum: plasma without fibrinogen & clotting proteins

 

ABO Blood Groups:

Type A Blood: has A antigen on red blood cell (rbc) surface; produces anti-B antibodies

Type B Blood: has B antigen on rbc surface; produces anti-A antibodies

Type O Blood: has neither A nor B antigen on rbc surface; produces anti-A & anti-B antibodies

Type AB Blood: has A antigen & B antigen on rbc surface; produces neither anti-A nor anti-B antibodies

 

Rh factor: additional antigen on rbc surface; if present, blood is "positive"; if not present, blood is "negative" for major Rh antigen (antigen D)

- example: type A+ blood has major Rh antigen; type A- blood does not have major Rh antigen on rbc surface

 

Transfusions:

Type A Blood: can receive type A & type O blood

Type B Blood: can receive type B & type O blood

Type O Blood: can receive only type O blood

Type AB Blood: can receive type A, type B, type AB & type O blood

 

But, Rh factor must also be considered:

Type A+ Blood: can receive type A+, type A-, type O+ & type O- blood

Type A- Blood: can receive type A- & type O- blood

 

Note: antibodies to Rh factor are only made after the first exposure; so, in theory, the first transfusion involving an individual with type A- Blood using type A+ blood should not generate a transfusion reaction (rejection)