Ch.24 The Immune System

WHAT ARE THE SIMILARITIES AND DIFFERENCES BETWEEN ACTIVE AND PASSIVE IMMUNITY?
Both are part of immune system. Both are artificial immunity, which is exposure to causative agent is not deliberate.
Active is active disease produces immunity. Passive is immunity passes from mother to fetus through placenta or from mother to child through mother’s milk.
Artificial immunity is exposure to causative agent is deliberate. Active is vaccination results in immunity. Passive is protective material developed in another individual’s immune system and given to previously non-immune individual. Active occurs when an individual’s own immune system responds to a harmful agent, regardless of whther that agent was naturally or artificially encountered. Passive immunity results when immunity to a disease that has developed in another individual or animal is transferred to an individual who was not previously immune. Active generally lasts longer than passive.

WHAT ARE PHAGOCYTES?
Ingest and destroy foreign cells or other harmful substances via phagocytosis. Neutrophils, monocytes, and macrophages are the examples.

WHAT ARE T CELLS AND B CELLS?
T cells: Produce cell-mediated immunity; kill invading cells by releasing a substance that poisons cells and also by releasing chemicals that attract and activate macrophages to kill cells by phagocytosis.
B cells: Indirectly, B cells produce humoral immunity; activated B cells develop into plasma cells; plasma cells secrete antibodies into the blood; circulating antibodies produce humoral immunity.

SUMMARY:
Invertebrates have only innate immunity, while vertebrates have innate and acquired immunity. The inflammatory response mobilizes innate defenses. Tissue damage triggers the inflammatory response. It can disinfect tissues and limit further infection. Lymphatic vessels collect fluid from body tissues, and return it as lymph to the blood. Lymph organs are packed with WBCs that fight infections. Our immune system responds to foreign molecules called antigens. The acquired immune system reacts to antigens and remembers an invader. Infection or vaccination triggers active immunity. We can temporarily acquire passive immunity by receiving premade antibodies. Two kinds of lymphocytes carry out the immune response, B cells and T cells. When an antigen enters the body, it activates only a small subset of lymphocytes. Those with complementary receptors. The selected lymphocyte cells multiply into clones of short-lived effector cells. Primary response occurs upon first exposure to an antigen and it is slower than the secondary response. The secondary immune response occurs upon second exposure to an antigen and it is faster and stronger than the primary immune response. In the cell-mediated immune response, an antigen presenting cell displays a foreign antigen and one of the body's own self proteins to a helper T cell. The helper T cell's receptors recognize the self-nonself complexes and the interaction activates the helper T cells. Cytotoxic T cells are the only T cells that kill infected cells. They bind to infected body cells to destroy them. AIDS results from infection by HIV. They attack helper T cells, opening the way for opportunistic infection. HIV mutates faster than any pathogen ever studied.



KEY TERMS:
- Innate defenses: first line of defense that can be found in all animals
- Interferons are proteins produced by virus-infected cells
- Lymphatic system: network of lymphatic vessels and organs
- Antigenic determinants: specific regions on an antigen to which antibodies bind
- Primary immune response: produces effector cells
- Secondary immune response: memory cells are activated by a second exposure to the same antigen
- Antibodies: secreted by plasma B cells into the blood and lymph
- mAb: produced by fusing and its name means all antibody-producing cells come from one cell
- Helper T cells: stimulate the humoral response
- Cytotoxic T cells: primarily responsible for the cell-mediated immune response

This is a diagram of HIV virus. HIV is a virus that is transmitted from person to person through the exchange of body fluids such as blood, semen, breast milk and vaginal secretions. Sexual contact is the most common way to spread HIV AIDS, but it can also be transmitted by sharing needles when injecting drugs, or during childbirth and breastfeeding. As HIV AIDS reproduces, it damages the body's immune system and the body becomes susceptible to illness and infection. There is no known cure for HIV infection.




http://www.youtube.com/watch?v=68I7JlVhuhY

This video talks about connection between HIV and AIDS. Especially when HIV becomes AIDS.




5 FACTS:
1) Both invertebrates and vertebrates have innate defenses against infection.
2) The acquired immune response counters specific invaders.
3) Clonal selection musters defensive forces against specific antigens.
4) Antibodies promote antigen elimination through several mechanisms.
5) Helper T cells stimulate the humoral and cell-madiated immune responses