Immune system

PART II

Any substance inducing an immune response is called an immunogen. Any substance stimulating production of antibodies which attempt to counteract that foreign substance is called antigen. Bacteria, viruses, and pollen may act as antigens. Thus, immunogens are also antigens.

Antibody is a substance produced in response to an infection. It combines with antigen and neutralizes it.

A complement and phagocytes take a special part in the immune system. Complement is a system of protein of blood serum, lymph, and tissue fluid. One of the complement constituent parts joins antibodies molecules and ensures the destruction of the cells containing antigens against which this antibodies have been produces.

Phagocytes are a type if white blood cells in body fluids and tissues. Destruction of harmful material, such as disease-causing bacteria or cell debris, by phagocytes is called phagocytosis.

White Blood Cells (leukocytes) help to protect the body against disease and infection. They are the main components of the body’s immune system. There are several kinds of WBCs including neutrophils, produced in the bone marrow; and monocytes, produced mostly in the spleen and the bone marrow.

When the body is injured or infected WBCs pass through the walls of the capillary blood vessels and congregate at the site of injury or infection.

Neutrophils and monocytes engulf and eat up invading bacteria and smalls particles breaking them up. Pus consists of an accumulation of dead neutrophils, monocytes, bacteria and tissue.

Lymphocytes are divided into several types: B-cells producing antibodies that attack specific viruses or bacteria; helper and killer T-cells which produce other substances to fight off foreign organisms and even kill infected cells; suppressor T-cells which slow down or stop the activities of B- and other T-cells after the elimination of the infection; and memory cells which remember the invading organism for a long time.

Immune response is usually carried out by body’s Lymphatic System.

I. Practise the pronunciation

capable	[´keıpəbl]
indjucing	[ın´dju:sıŋ]
immunogen	[ı´mju:nə,dɜı:n]
counteract	[kəuntə´rækt ]
antigen	[´æntı ̖dɜı:n ]
virus	[ ´vaırəs]
pollen	[´pɔlın]
neutralize	[´nju:trəlaız]
complement	[´kɔmplımǝnt ]
phagocyte	[´fæɡǝsaıt]
constituent	[kǝn´stıtjuǝnt ]
ensure	[ın´ʃuə ]
phagocytosis	[¸fæɡɔsaı´tousıs ]
leukocyte	[´lju:kəsaıt]
neutrophil	[´nju:trǝfıl ]
lymphocyte	[´lımfǝsaıt ]
monocyte	[´mɔnɔsaıt ]
congregate	[´kɔŋɡrıɡeıt ]
engulf	[ın´ɡʌlf ]
accumulation	[ǝ¸kju:mju´leıʃn ]
suppressor	[səp´resə ]
eliminate	[ ı´lımıneıt]
initiating	[ı´nıʃıeıtıŋ ]