Tuesday, April 28, 2009

Chapter 43- The Body's Defenses

In innate immunity, recognition and response rely on shared pathogen traits

Innate immune responses include barrier defenses as well as defenses to combat pathogens that end the body

1. Barrier defenses skin and the mucous membranes cover the surface and line the openings of the animal body, and they provide an external barrier against infecting agents

First Line of Defense
Specifically, skin, antimicrobial proteins are in the saliva, cilia lines the lungs to sweep invaders out, gastric juice of the stomach kills most microbes, and symbiotic bacteria in the digestive tract also serve as first line of denfense

Microbes that get through the skin-- for instance, in a cut-- encounter certain types of white blood cells called neutrophils that ingest and destroy them in a process called phagocytosis

Here is a link to a video showing neutrophil phagocytosis


2. Cellular innate defenses combat pathogens that get through the skin-- for example, in a cut. They include phagocytic white blood cells and antimicrobial proteins.

Phagocytic White
Blood Cells
  • Neutrophils are white blood cells that ingest and destroy microbes in a process called phagocytosis
  • Monocytes are another type of phagocytic leukocyte. They migrate into tissues and develop into macrophages, which are giant phagocytic cells
  • Eosinophils are leukocytes that defend against parasitic invaders such as worms by positioning themsleves near the parasite's wall and discharging hydrolytic enzymes

Antimicrobial Prot

Inteferon proteins provide innate defense against viral infections. They cause cells adjacent to injected cells to produce substances to inhibit viral replication

The complement system consists
of roughly 30 proteins with a variety of functions. One function is to lyse invading cells.

The major histocompatibility complex, or MHC, is the mechanism by which the immune system is able to differentiate between self and nonself cells. The MHC is a collection of glycoproteins that exists on the membranes of all body cells.

3. The inflammatory response occ
urs where physical injury occurs to a tissue, and occurs in response to chemical signals (Second line of defense). For example, histamines are released by basophils and most cells (two ypes of leukocytes) in response to injury. Histamines trigger the dilation and permeability of nearby capillaries. This aids in delivering clotting agents (white blood cells) to the injured area. Vasodilation causes redness, and increase in temperature, and and swelling. Histamines cause watery, itchy eyes, and sneezing. We fight histamine reactions with antihistamines.

The third line of defense is the immune response and it differs from the inflammatory response in that it targets specific antigens.

4. Natural Killer (NK) cells help recognize and remove diseased cells

In acquired immunity, lymphocyte receptors provide pathogen- specific recognition

Vertebrates have two types of: B lymphocytes (B cells) which proliferate in the bone marrow, and T lymphocytes (T cells) where lymphocytes mature in the thymus. They circulate through the blood and lymph, and both recognize particular microbes and are said to show specificity.

Antigens are foreign molecules that elicit a response by lymphocytes

Antibodies are proteins secreted by B cells in an immune response. Each anitibody is specific to a particular antigen. There are five classes of anitbodies (or immunoglobins): IgA, IgD, IgE, IgG, IgM.

Antigen receptors are located on the antigen and allow B and T cells to recognize them as antigen receptors on T cells are called T cell receptors, which combat the antigen, and the other consists of memory cells, which are long-lived and bear receptors for the same antigen.

Plasma cells are B cells that release their specific antibodies which then circulate through the body, binding to antigens.

Memory cells are lon-lived B cells that do not release their antibodies in response to the immediate antigen invasion. Instead, the memory cells circulate in the body and respond quickly to eliminate any subsequent invasion by the same antigen. This mechanism provides immunity to many diseases after the first occurence of the disease.

Here is a link to a video about white blood cells, T-cells, NK cells, and cancer cells


Multiple Choice Questions

1. Which if these cells produce and secrete antibodies?

a) macrophages
b) cytotoxic T cells
c) helper T cells
d) bacterial cells
e) plasma cells

2. What kind of white blood cells defend against parasitic invaders?
a) basophils
b) monocytes
c) eosinophils
d) neutrophils
e) histamines

3. ________ proliferate in the bone marrow and ________ mature in the thymus.

a) B cells, T cells
b) NK cells, T cells
c) T cells, B cells
d) B cells, NK cells
e) NK cells, B cells

4. Histamine is secreted by ________.

a) eosinophils
b) monocytes
c) basophils
d) T lymphocytes
e) B lymphocytes

Answers: 1. e, 2. c, 3. a, 4. c

Notes reposted from March 30th, due to technical difficulties with my blog account.

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