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Blood & Immunity. Notes. First line of defense. physical barriers – skin and membranes that line body cavities skin provides a protective barrier that cannot normally be penetrated by bacteria or viruses . chemical barriers – sweat, tears, saliva, mucus, stomach acid

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Blood & Immunity

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first line of defense
First line of defense
  • physical barriers – skin and membranes that line body cavities
  • skin provides a protective barrier that cannot normally be penetrated by bacteria or viruses.
  • chemical barriers – sweat, tears, saliva, mucus, stomach acid
  • The skin also defends itself in the form of acidic secretions (pH around 3-5)
  • Lysosomes secreted by tears, saliva, mucous and sweat destroys the cell walls of bacteria
second line of defense the inflammatory response
Second line of defense: the inflammatory response
  • Foreign material penetrates the skin through an injury
  • Infected cells release warning chemicals in the area, this causes blood flow to increase to that area
  • More blood causes swelling, redness, warmth, pain, and more importantly phagocytes – the release of special leukocytes - neutrophils and macrophages!

The macrophage will extend long pseudopods and engulf the invading microbe

  • Macrophages eat up the bacteria and damaged cells. Enzymes will be secreted by the macrophage which will destroy the microbe and pus is formed (phagocytes, bacteria, dead cells, body fluid)
  • Neutrophils are attracted to chemical signals given off by cells that have been damaged by microbes. The Neutrophils will squeeze out of capillaries and migrate toward the infected tissue (chemotaxis). The neutrophil will then engulf the microbe and secrete enzymes to destroy it.

As pathogen is removed, number of injured cells decreases, amount of warning chemical subsides, inflammation dies down, and the wound heals

dammage to tissues fig 2
Dammage to Tissues – fig.2

(a) At the first sign of injury, chemical signals are released by the foreign invader. Other chemicals— histamines and prostaglandins—are

released by the cells of the body.

(b) Chemical signals cause the capillaries to dilate. Blood flow increases and the

capillaries become more

permeable. Other

chemicals attract

phagocytic cells and

specialized white blood


(c) Phagocytes engulf and digest the invaders and cellular debris, which promotes healing of the tissues.

second line of defense for viruses
Second line of defense: for viruses
  • infected cells secrete interferon, warning chemical in the area
  • nearby healthy cells produce enzymes that block the reproduction of the viruses, thereby making themselves immune to the virus
  • the body uses a fever as a system-wide response to infection. Neutrophils and macrophages digest foreign invaders ad release chemicals into to your blood stream
  • when these chemicals reach your hypothalamus in your brain, they reset the body’s thermostat to a higher fever
  • these temperatures help to prevent the proliferation of the infectious organism
third line of defense the immune system
Third line of defense: the immune system

total body attack against pathogen (bone marrow, WBC, lymphatic system, tonsils, thymus, and spleen)!!!

  • The immune response can be divided into the primary and secondary response.
  • Macrophages reside in body tissue or in the lymphatic system and will recognize foreign organisms.
third line of defense continued
Third line of defense - continued
  • Primary response – first 5 days, antigen is recognized by B and T cells and the body fights back by creating cells to fight the antigen so that in 10 to 15 days there is a rise in antibodies.
  • Secondary response – if the same antigen returns, high level of antibodies results in 1 to 2 days because the body remembers and retains cells to fight the antigen.
important cells in immune response
Important cells in immune response:

Complement proteins, T cells and B cells all play an important role in fighting off bacteria

  • Complement proteins - Under normal conditions, complement proteins are present in the circulatory system in an inactive form; will recognize foreign materials that enter the body
  • T cells – produced in the bone marrow and stored in the thymus gland; seeks out intruders and signals the attack; identifies invaders by antigen markers

B cells – produced in the bone marrow; produce antibodies in response to the T cells; each B cell produces a single type of antibody which is displayed on its membrane; some will differentiate into super-anitbody producing plasma cell, which produce as many as 2000 antibody molecules every second

Figure 5

Sugar-protein complexes located on the cell membrane act as markers. T cells distinguish the markers on the body’s cells from those of invading cells.

steps to immune response for bacteria
Steps to immune response for bacteria:
  • The appearance of foreign organisms in the body activates antimicrobial plasma proteins called complement proteins.
  • Marker proteins from invading microbes activate the complement proteins, which serve as messengers to initiate an attack on the cell membrane of fungal or bacterial cells.

Some of the activated proteins trigger the formation of a protective coating around the invader, which immobilizes it.

  • B cell binds to an antigen and a macrophage comes along and digests it exposing the insides of the antigen to the helper T cell.
  • When the helper T cell recognizes the antigen too, it stimulates the B cell to produce antibodies.

The antibodies bind to the antigens and that attracts more phagocytes, which eat the antigen.

  • As your body wins the war against the antigen, suppressor T cells secrete a substance to stop the response.
  • The memory B cells live for a lifetime and will start the secondary immune response if the same antigen tries to infect you again.
steps to immune response for virus
Steps to immune response for virus:
  • a single T cell recognizes and binds to the antigen (notice there is no B cell present).
  • A macrophage takes in the combination to expose the virus to a helper T cell, which stimulates the initial T cell to divide. Resulting from cellular division are memory T cells and killer T cells. Killer T cells bind to antigens on infected cells and cause them to burst open. Without the cell, the virus can not replicate itself.
types of immunity
Types of Immunity
  • Active Immunity – body produces its own antibodies or killer T cells, permanent
  • Passive Immunity – body is given antibodies taken from another organism, temporary
  • Edward Jenner – developed the first vaccine (passive immunity) for small pox. He observed that milkmaids did not get small pox, the deadly disease that was going around, but rather, they got cowpox, a mild form of pox. Jenner hypothesized that the cowpox was protecting them from the small pox, but he did not know how. So, he took a chance and infected a farm boy with the cowpox virus and he survived. He then, infected others and they also survived. A vaccine contains the mild or inert form of the disease that the vaccine is to protect you from.
aids and immune disorders
AIDS and Immune Disorders
  • AIDS = Acquired Immune Deficiency Syndrome, caused by a virus called the human immunodeficiency virus or HIV.
  • HIV enters your helper T cells and replicate and bursts the cell only to infect more cells. Without your helper T cells, your immune system can not work.
  • Helper T cells recognize antigens presented by macrophages. Then they stimulate killer T cells, memory B cells and antibody production, depending on the type of invasion. No helper T cells, no defense. You can die from a cold, theoretically.
aids hiv
  • There is a latent period with this disease, months or years can pass without symptoms. Once activated, symptoms can include, swollen lymph glands, fever, weakness, weight loss, frequent infections (because immunity is compromised), memory loss, loss of coordination, partial paralysis, and mental disorder.

Figure 8

HIV has a shape that provides access to the T cell. The T cell engulfs HIV, unlike most other viruses.

spread of aids
Spread of AIDS
  • intimate sexual conduct, due to the exchange of WBC in body fluids
  • blood to blood contact, due to the exchange of WBC in blood
  • Prevention - Avoid 1 and 2 (above)
  • Treatment – no cure
immune disorders
Immune Disorders
  • Allergies – due to an immune response to a non-threatening antigen and the release of histamine.
  • Autoimmune diseases – body sees itself as an antigen and attacks it with an immune response. Rheumatoid arthritis (attack the joints), MS (attack nerve cells), and Lupus (attack organs) are examples of autoimmune diseases.