NonSpecific Resistance

Nonspecific resistance refers to bodily defenses that protect us from almost any kind of 
pathogen. Contributors to nonspecific resistance are the skin and mucous membranes, 
phagocytosis, inflammation, fever and the production of antimicrobial substances 
other than antibodies.

   I. Mechanical and Chemical Barriers
	 A. Intact skin & mucous membranes - prevent penetration
	 B. Mucus and cilia - sweep materials from nose and throat
	 C. Tears, Saliva, Urine, Vaginal Secretions - all move
	    materials out of the body in a cleansing action
	 D. Sebum, Lysozyme
	 E. pH
	    1. Stomach acid
	    2. bile, duodenal enzymes
	    3. acidity of vaginal tract
	 F. Interferon - nonspecific viral inhibitor
  II. Phagocytosis
	 carried out by white blood cells or derivatives of white
	 blood cells such as modified Monocytes (Macrophages)

	PHAGOCYTOSIS
                            /    \
                          /        \
          MICROPHAGES      MACROPHAGES
      especially neutrophils      wandering macrophages; fixed
                 |                macrophage or histiocytes;
                 |                Mononuclear Phagocytic System
                 |                or Reticuloendothelial System
                 |                       |
                                    
phagocytic against microbes       phagocytic against dead & dying
during the initial phase of       microbes and worn out red blood
infection                         cell as infection subsides;
                                   
                                  also involved in cell-mediated
                                  immunity

Generally the phagocytic cells are polymorphonucleated cells (PMN) such as 
neutrophils or agranulocytic monocytes. Macrophages (derived from monocytes) 
make up the MPS or RES and are specialized as WANDERING (macrophages of 
spleen, bone marrow, lymph nodes, brain, connective tissue and lungs) or 
FIXED (Kupffer cells of the liver) cells.

@NCI, NIH "Understanding the Immune System", Click on this link for image
III. Circulatory System
	Fluid portion of blood is called PLASMA and contains the formed 
        elements (cells and cell fragments). Plasma with fibrin or clotting
        factors removed is called SERUM. FORMED	ELEMENTS are the red blood 
        cells (ERYTHROCYTES), white blood cells (LEUKOCYTES), and platelets 
        (THROMBOCYTES).

	White blood cells are divided into two categories based on Wright's staining:

	A. Granulocytes - contain prominent lysosomal granules
	   1. Neutrophils - make up 60-65% in normal differential
		 count; highly phagocytic; capable of diapedesis
	   2. Basophils- make up approximately 0-2% of normal differential;
                 non phagocytic; involved in allergic reactions through 
                 the release of histamine, heparin, serotonin, leukotrienes
	   3. Eosinophils - make up approximately 0-4% of normal
		 differential count; somewhat phagocytic; capable of
		 diapedesis; increase in numbers during hypersensitivity 
                 reactions and parasitic infections; may be attracted by 
                 chemotactic agents released by basophils

	All three of the above are considered to be Polymorphonucleated 
        cells (PMN).

	B. Agranulocytes - no obvious granules upon staining
	   1. Monocytes - make up 5-8% of normal differential; poorly 
                 phagocytic until stimulated - in the tissues
		 the monocytes are converted into macrophages when 
		 stimulated; the largest and most long-lived WBC's
	   2. Lymphocytes - make up 25-30% of normal differential;
		 non phagocytic; involved in antibody and T cell 
		 formation when stimulated

  IV. Lymphatic System
	 consists of fluid, vessels, and organs; fluid is known as
	 LYMPH and consists of water, plasma, proteins, electrolytes
	 and white blood cells (Lymphocytes); Lymphocytes migrate 
 	 between blood and lymph; entry to lymph from the blood is
	 in the lymph nodes
		examples of lymphatic tissues and organs include: 
		tonsils, adenoids, spleen, Peyer's Patches of the 
		intestinal mesentery, appendix, lymph nodes

   V. Antimicrobial Substances from Animal Tissues and Fluids
	 A. Complement - found in serum; family of proteins which
	    lyse invading microbes when stimulated or activated;
	    hemolytic when activated; work with various antibodies
	 B. Lysozyme - found in tears, sweat, saliva, mucous secre-
	    tions, white blood cells - lyse Gram + bacteria
	 C. Interferon - released from virus infected cells; activa-
	    tes adjacent cells and interferes with viral replication
	 D. Spermine - found in seminal and pancreatic fluids; bac-
	    tericidal for a variety of Gram + pathogens
	 E. Sebum - produced in sebaceous glands; bactericidal and 
	    fungicidal; becomes active after puberty

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