NATS 1675 Lecture Notes - Lecture 23: Immunoglobulin A, Glycolipid, Passive Immunity

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8 Apr 2016
NATS 1675 LECTURE #23 The Lymphatic System and Immunity continued
Professor: Robert Crippen
Body Defenses against Infections
The most important aspect in the lymphatic system is fighting diseases
An infection is a condition caused by the presence of a disease causing agenta
Pathogens include viruses and microorganisms such as bacteria (Refer to Figures 8.1 &
8.4 in the textbook), fungi, protists and various parasites
The body’s defense mechanisms help to prevent the entrance of pathogens or act to
destroy them if they do enter the tissue
These defense mechanisms are divided into two broad categories: non-specific
[preventing entry or fight the infections when it occurs] and specific [dealing primarily
with immunity; your body will fill up with antibodies & store information for a later time so
when you get infected, your body will gear faster for you to feel better]
Non-specific mechanisms are general in that they protect against many types of
Specific mechanisms provide protection against particular pathogens, and they are
responsible for the type of resistance we call immunity
Non specific Mechanisms
1) Species resistance
It is a given kind of organism develops diseases that are unique to it. ex., animal
species other than human are generally resistant to the microorganisms that
cause gonorrhea and syphilis
2) Mechanical barriers
It is the skin and mucous membranes create mechanical barriers against the
entrance of infectious agents
3) Enzymatic actions
It is the presence of certain enzymes in various body fluids acts against disease
causing agents. ex., pepsin and hydrochloric acid (low pH) in the stomach is
lethal to many pathogens
Tears contain an enzyme that has an antibacterial action
4) Resident Bacteria
They are normal microbes that reside in the mouth, intestine and elsewhere act
as a significant chemical barrier to infection by depleting available nutrients and
releasing their own wastes
Abusing antibiotics can make an individual susceptible to pathogens by killing off
the normal (good) microbes
5) Interferon
It is a group of proteins produced by cells infected with a virus
It binds with non-infected cells preparing them for a possible attack
6) Inflammation or Inflammatory reaction
It is an inflamed area can be distinguished by redness, heat, swelling and pain
This is a complicated process involving the release of chemicals by certain cells,
attraction of phagocytic white blood cells to the area and stimulation of the
immune system
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Inflammation helps to prevent the spread of infection to nearby tissues
7) Phagocytosis
It is the engulfing and destruction of foreign particles, cells, virus-infected cells
and tumor cells by various types of white blood cells: neutrophils, monocytes and
8) Fever
This may be a component of the non-specific defense system
Normal body temperature (37o C) is regulated by the hypothalamus in the brain
that contains a thermoregulatory control centre (a “thermostat”)
This “thermostat” is reset upward by the chemical endogenous pyrogen
secreted by leukocytes
The secretion of this chemical can be stimulated by another chemical,
endotoxin, released by certain bacteria, other infections and inflammations
High fevers are dangerous: they can damage tissues, lead to blood vessel
damage in the brain and convulsions
Some researchers believe that mild to moderate fever, however, may be
beneficial in recovering from bacterial infections
The reasons may be either by increasing the body’s metabolic rate at which the
body can carry out the processes to eliminate infections, or that an elevated body
temperature may interfere with the nutritional requirements of some bacteria
Specific Mechanisms
Immunity is the resistance to specific pathogens or the toxins they release
It involves a number of immune mechanisms
Certain white blood cells, ex., lymphocytes and macrophages, recognize the presence
of particular foreign substances (antigens) and act against them
Macrophages are mature monocytes
They are large phagocytic cells that become fixed to various tissues or to the inner walls
of blood vessels and lymphatic vessels
Macrophages are capable of consuming 100 bacteria or viruses and still survive
Lymphocytes and Monocytes (Macrophages)
They are the two types of agranular leukocytesone of the two categories or groups of
Macrophages are relatively non-motile
They can divide or reproduce themselves and are found in organs such as lymph nodes,
spleen, liver and lungs
More about Lymphocytes
Prior to birth undifferentiated lymphocytes (called lymphoid stem cells) are released and
carried away from the red bone marrow by the blood to other locations in the body where
they become differentiated (they become structurally and functionally specialized)
About ½ reach the thymus and remain there for some time
Here they differentiate and become T-lymphocytes or T-cells
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