MICROBIOLOGY AND IMMUNOLOGY

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MICROBIOLOGY AND IMMUNOLOGY 



Definitions of Terms 
·         Microbiology-study of minute organisms that cannot be seen by naked eyes
·         Immunology-Study of the body mechanism involved in disease prevention so that the body can resist infections.
·         Bacteriology-Study of bacteria
·         Virology-Study of viruses
·         Mycology-Study of fungi
·         Morphology-Physical appearance of micro organism
·         Phagocytosis.-The process of engulfing foreign substances in the body by use of specialized cells and destroy it completely.


Define the basic immunology 
Immunology  is the study of body defence mechanisms. Its derived from latin word immunitas meaning freedom from. This gives the basis of immunology.The mainfunction of immune system is to prevent or limit infections by microorganisms.For example,
The first line of defence against microorganism is the intact skin and mucosa membrane.


Describe types of immunity
The defence mechanisms in the body is divided in two as:-
  • Natural immunity(non-specific
  • Acquired immunity(specific).
NATURAL IMMUNITY(Non- specific)
This is the first line of the body defence mechanism.
It consists of the following:-
a)Mechanical barriers-This includes skin, lining of the gut, mucosa of the respiratory tract  and genital areas. Nasal hairs act as filters.The action of coughing and sneezing removes the microorganism.
b)Chemical barrier-These are secretions that consists substances whish have anti-microbial actions. Examples; lysosomes found in eyes, genital areas, respiratory tract, The salty fatty acid, sebam found in skin secretions, blood, HCL in the stomach and tissue components(complement).
c)Phagocytosis-This is when cells caslled phagoctytes engulf and destroys an organism or other foreign bodies by digesting it with enzyme lysosomes or phagocyte is attracted to the site of infection by a chemical substance called to as chemotactic factor.Examples of phagocytic cells include;Neutrophils circulating in the body,macrophage in lympnodes,Histocytes in connective tissues,microgial cells in the brain, kupffer cells in the liver,monocytes in blood
d)Antimicrobials –These are commensal flora protecting the body from infection by stopping growth of potential pathogenic organisms by:-
·         occupying the attachment
·         site.competing for essential nutrients
·         producing substances anatagonistic to other bacteria e.g.colicines.

ACQUiRED IMMUNITY(specific)
.This is the second line of defence mechanism after the natural.It is divided into active  acquired or passive acquired.

Active acquired immunity
This immunity can be Humoral(antibody mediated) or cellular(cell mediated-B-and T -cells) or both
This is when the body responds to foreign substance or microorganisms by producing antibodies.
The immunity is produced as a result of antigenic stimulation.E.g. infections,Antibody or cell mediated(T and B cells),vaccination.

Passive acquired immunity
This is when antibodies formed from another human or animal  are introduced into the body.This gives the body protection against foreign substance or microorganism.
It occurs naturally with passage of certain antibodies across the placenta to the foetus and also the transfer of maternal antibodies in breast milk after birth.

 Acquired immunity


 ACTIVE
-infection (Antibody or cell  mediated)
-Vaccination

 PASSIVE
-Transplacental or breast milk(Antibody mediated
-Administration of immune serum or cells


 HUMORAL IMMUNITY
These are plasma protein circulating antibodies. They are specifically attached to antigen(bacteria, virus and cells).They are produced by B-cell. The antibodies produced are       IgM,   IgG, IgD, IgE, IgA.



IgG
  • Consist of one sub unit and has  two Ag combining sites
  • Found in blood and tissue spaces.
  • Crosses placenta barrier
  • Its pre-dorminant in the circulating system(major)
  • Secondary line of protection

IgM
  • Consists of 5 subunits
  • Has  10 antigen binding sites
  • Found in blood circulation
  • Its the main antibody formed after infection(primary response )

IgA
  • Consists of 2 subunits with 4 antigen binding sites
  • Found in body secretions

IgE
  • Found in tissue and little in blood
  • Its found in high quantities in patients with parasitic infection, asthma or allergic reactions

IgD
  • Function is not clear.
  • Found in leukemic patients
  • Has short half life in serum

CELLULAR  IMMUNITY
Mediated by cell. The cells involved are:
  • T-Cells-found in T-lymphocytes-
They are divided in to the following subsets;-
o   T-helper cells
o   T-cytotoxic cells
o   T-suppressor cells
o   T-delayed hypesensitivity cells
  • B-cells.-found in body fluids

List the common immunological/serological reactions
·         latex agglutination-Visible clamping together of bacteria,cells or particles by an antigen combining with its specific antibodies.
·         precipitation –This is a test that involves reactions of soluble antigens. when it reacts with antibody it forms insoluble deposits(precipitate)
·         Immune-chromatographic test
·         Flocculation- This is a test that involves reactions of soluble antigens. when it reacts with antibody it form loose clumps of  precipitate.(floccules)


Importance of immunological investigation
·         To detect Antibodies that are responsible for an infection

List common disorders and conditions associated with serological test 
·         Disorders: -
·         syphilis  
·         hepatitis;

·         Condition: -
·         pregnancy

Key Points 
Types of immunity
Natural and acquired

Humoral Antibodies
IgG,IgM,IgD,IgE,IgA

List the common immunological/serological reactions
·         latex agglutination
·         Flocculation tests
·         Immune-chromatographic test


Evaluation:

  • Define microbiology,Immunology,precipition
  • List two types of immunity
  • List 5 types of humoral antibodies
  • Mention 2 cells involved in cellular immune system

References:
·         Ivan M. Roitt & Peter J.Delves ROITTS ESSENTIAL IMMUNOLOGY, 10th Edition, (2004) Replika press  Pvt.ltd ,india
·         Monica Cheesbrough – MEDICAL LABORATORY MANUAL FOR TROPICAl Countries, part 2, Edition (2003) Cambridge University press,international sales department.
·         Monica Cheesbrough – MEDICAL LABORATORY MANUAL FOR TROPICAL COUNTRIES, volume 2, Microbiology, Edition (1984) Cambridge University press.
·         Warren Levinson. MD,PHD– Medical Microbiology & Immunology edition (2004) Mc Graw –HillCompanies

·         Satish Gupte THE SHORT TEXT BOOK FOR MEDICAL MICROBIOLOGY(including parasitology) 10th Edition, (2004) Replika press  Pvt.ltd ,india 

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