Disease and Immunity

Explain why antibiotics are effective against bacteria but not against viruses.

Antibiotics block specific metabolic pathways in bacteria. Bacteria are very different to human cells so human cells are not affected. Viruses require host cell to carry metabolic processes for them and so antibiotics cannot be used to treat viruses. Harming the virus would harm the human cells.

What name is given to the molecules that bind to foreign proteins that enter the body?

Antibodies

Which of the following statements about antibodies is correct? A. Antibodies are polypeptides B. Antibodies are produced by the bone marrow. C. Antibodies are pathogenic foreign substances D. Antibodies kill bacteria but not viruses

Antibodies are polypeptides

Which term describes a molecule capable of triggering an immune response?

Antigen

When a pathogen is ingested by a phagocyte, which event occurs first?

Antigen presentation by the phagocyte

What stimulates the production of antibodies?

Antigens

Explain (in detail) the stages of antibody production.

Antigens stimulate an immune response via the production of antibodies When a pathogen invades the body, it is engulfed by wandering macrophages which present the antigenic fragments on its surface This macrophage becomes an antigen-presenting cell, and presents the antigen to helper T cells (TH cells) The TH cells bind to the antigen and become activated, and in turn activate the B cell with the specific antibody for the antigen This B cell clones and differentiates into plasma cells and memory cells The plasma cells produce high quantities of specific antibody to the antigen, whereas memory cells survive in the bloodstream for years. Upon re-exposure to the antigen, memory cells initiate a faster and stronger response and thus confer long-term immunity

What is required to produce monoclonal antibodies?

B-lymphocytes and tumour cells

Which of the following represents the correct sequence of events when the body is responding to a bacterial infection? I. Antigen presentation by macrophages II. Activation of B-Cells III. Activation of helper T-cells

B. I, III, II

How can active immunity be acquired?

By having the disease

What is required for a blood clot? I. Platelets II. Clotting factors III. Antibodies IV. Fibrinogen

C. I, II, and IV only

Outline the principle of challenge and response, clonal selection and memory cells as a basis of immunity.

Challenge and Response When the body is challenged by a foreign pathogen it will respond with both a non-specific and specific immune reaction The body is capable of recognising invaders as they do not possess the molecular markers that designated all body cells as 'self' (MHC class I) Non-specific immune cells (macrophages) present the foreign antigens to lymphocytes as examples of 'non-self' (on MHC class II) These lymphocytes can then respond with the production of antibodies to destroy the foreign invaders Clonal Selection Each B lymphocyte has a specific antibody on its surface that is capable of recognising a specific antigen When antigens are presented to B cells (and TH cells) by macrophages, only the B cell with the appropriate antibody will become activated and clone The majority of B cell clones will differentiate into antibody-producing plasma cells, a minority will become memory B cells (BM cells) Because pathogens may contain several antigenic determinants, several B cell clones may become activated (polyclonal activation) Memory Cells Because the adaptive immune response is dependent on clonal expansion to create sufficiently large amounts of antibodies, there is a delay between initial exposure and the production of antibodies When a B cell does divide and differentiate into antibody-secreting plasma cells, a small proportion of clones will differentiate into memory cells Memory cells remain in the body for years (or even a lifetime) If a second infection with the same antigen occurs, the memory cells react faster and more vigorously than the initial immune response, such that the symptoms of the infection do not normally appear Because the individual no longer presents with the symptoms of infection upon exposure, the individual is thus said to be immune

Describe the process of blood clotting.

Clotting is a mechanism that prevents the loss of blood from broken vessels - Damaged cells and platelets release chemical signals called clotting factors, which trigger a coagulation cascade: o Clotting factors convert the inactive prothrombin into the activated enzyme thrombin o Thrombin catalyzes the conversion of the soluble plasma protein fibrinogen into an insoluble form (fibrin) o Fibrin forms an insoluble mesh of fibers that trap blood cells at the site of damage - Clotting factors also cause platelets to become sticky, which then adhere to the damaged region to form a solid plug called a clot - The clot prevents further blood loss and blocks entry to foreign pathogen

Which types of cells in the immune system to destroy body cells that have been infected by viruses?

Cytotoxic T-Cells

Which is not true of active immunity? A. It can be produced by exposure to a disease causing organism B. It can be produced artificially. C. It can be produced by a virus. D. It can be transferred via the colostrum

D. It can be transferred via the colostrum

Explain the role of antibody production with regard to vaccinations.

Each lymphocyte makes one type of antibody. Antibodies are found on the surface of the lymphocyte. Pathogen have antigens on their surface. The antigens bind to the antibodies. Lymphocyte becomes active and makes clones of itself. The clones make more of the specific antibody.

A blood clot contains a network of protein. What is the protein?

Fibrin

Which factors related to mucous membranes protect the body against microbes? I. Production of lysozyme II. Secretion of alkaline solutions III. Trapping of microbes

I and III only

Where in a cell are antigens found?

In the plasma membrane

Which cells activate helper T-cells by antigen presentation?

Macrophages

Which type of cell is responsible for secondary immune responses to a pathogen?

Memory cells

Outline the production of monoclonal antibodies.

Monoclonal antibodies are antibodies derived from a single B cell clone An animal is injected with an antigen and produces specific plasma cells The plasma cells are removed and fused (hybridised) with tumor cells capable of endless divisions (immortal cell line) The resulting hybridoma is capable of synthesising large quantities of specific antigen, for use in diagnosis and treatment

What are two effects of HIV on the immune system?

Reduction in antibody production and decrease in active lymphocytes

Outline the effects of HIV on the immune system.

The HIV virus (which causes AIDS) destroys a type of lymphocyte which has a vital role in antibody production. Over the years this results in a reduced amount of active lymphocytes. Therefore, less antibodies are produced which makes the body very vulnerable to pathogens. A pathogen that could easily be controlled by the body in a healthy individual can cause serious consequences and eventually lead to death for patients affected by HIV.

What does the nucleus of a human lymphocyte contain?

The whole genetic information for a human

How do vaccines give immunity to infectious diseases?

They produce an immune response

What are fused in the production of monoclonal antibodies?

Tumor cells and B-cells

Why do antibiotics kill bacteria but not viruses?

Viruses do not have a metabolism

What prevents antibiotics from being effective against viruses?

Viruses have no metabolism

Distinguish between active & passive immunity and natural & artificial.

active immunity- production of antibodies by the organism itself passive immunity-acquisition of antibodies from another organism natural immunity- immunity due to infection/ acquisition from another person; immunity that is present without prior immunization. artificial immunity- body is given immunity to a disease by intentional exposure to small quantities of it.

Which type of immunity usually results from vaccination?

active, artificial

Distinguish between primary immune response and secondary immune response

primary: body is first exposed to antigen, lymphocyte is activated. secondary: same antigen is encountered at a later time. It is faster and of greater magnitude.