types of immunity

Microbiology/Immunology lect.1-
Ass.Professor Dr.Mohammed A.K.AL-SA ADI
Introduction:
The study of the defense mechanisms of the body against foreign substances including microorganisms that enter into the body constitutes the subject immunology. Immunology began as a branch of microbiology .The study of infectious disease and the body s response to the infections led to the development of immunology. Immunity(immunitas-a Latin word ;freedom from disease)is due to the existence of a complex defense system in the human body ,called immune system .The term immunity is concerned with the state of being resistant (or immune)to foreign substances such as microbes.
General functions of immune system:
1-Defence against foreign invaders .
2-Autotolerance(unresponsiveness to the self tissues)
3-Surveillance:Recognition and clearance of internal antigens (old, damaged ,or mutagenic cells,…).
Types of immunity:
Immunity can be classified according to their specificity into:
a-Non-specific(innate) immunity b-Specific(acquired or adaptive) immunity
a- Non-specific (innate)immunity :
the elements of the non-specific (innate)immunity include:
(1)-Anatomoical barriers (e.g. skin, intestinal movement, and oscillation of respiratory tract).(2)-Chemical factors: Include fatty acids in sweat ,lysozyme , phospholipids, pH, defensins which are the antimicrobial polypeptides secreted by a wide variety of host cells .(3)-Physiologic barriers :e.g; fever response to infection inhibits growth of many microbes.(4)-Biological factors: Include the normal flora of the (skin ,genitourinary tract, and GIT) can prevent the colonization of pathogenic microbes by secreting toxic substances or by competing with pathogens for nutrient or attachment to host cells .