Deck 47: The Immune System in Animals

Question 1

What is the primary difference between the innate and adaptive responses?

A) The innate response does not distinguish between pathogens, while the adaptive response does.
B) Only the innate response is triggered by antigens.
C) The adaptive response generates immunological memory and is more specific than the innate response.
D) The innate response does not kill cells; the adaptive response does.

Answer 1

The primary differences between the innate and adaptive response are: -
1. An antigen is a foreign molecule that can initiate an immune system response.
2. The cells involved in innate immunity are non specific in their response to antigens.
3. Innate immunity present before the onset of infection is adaptive immunity and do not develop till antigenic stimulus.
Hence the correct answer is (c) the adaptive response is specific and is "remembered"; the innate response is nonspecific.

Question 2

The overall role of the inflammatory response is to

A) contain and eliminate foreign cells and material at the site of infection.
B) increase heat at the site of infection to activate enzymes used in the immune response.
C) produce antibodies that bind to invading cells and eliminate them.
D) increase blood flow at the site of the wound to flush out invading pathogen.

Answer 2

The inflammatory response is an innate immune response. The inflammatory response defends against all types of microbes. The inflammatory response is nonspecific. The inflammatory response has several steps.
An open wound allows bacteria to enter the body. Platelets secrete proteins to the wounded site. These proteins prevent more bacteria from entering the body. In addition, these proteins prevent bleeding and blood loss.
Several leukocytes play important role in destroying the invading bacteria. For example, macrophages secrete chemokines. As a result, the wounded site has high concentration of chemokines. The chemokines attract other leukocytes to the wounded site.
The mast cells secrete histamines. Histamines constrict blood vessels. Consequently, less blood is lost. The mast cells also secrete other molecules. These molecules dilate far away blood vessels. The dilated blood vessels facilitate the entry of more leukocytes. These leukocytes include macrophages and neutrophils.
Neutrophils and macrophages contain digestive enzymes. These leukocytes engulf the bacteria. Consequently, these leukocytes destroy the bacteria.
The macrophages secrete cytokines. Cytokines have three important functions. First, the cytokines trigger repair of the wounded tissue. Second, the cytokines increase body temperature. The increase of body temperature facilitates the healing process. Third, the cytokines stimulate the bone marrow. The stimulated bone marrow would produce more leukocytes. Thus, the cytokines ensure that adequate leukocytes are present. The main goal is to destroy all the invading bacteria.
Hence, the correct option is (a) contain and eliminate foreign cells and material at the site of infection.
Macrophages secrete cytokines. Cytokines would increase heat at the infected site. The increase in body temperature initiates fever. The main goal is to facilitate healing. However, the overall role of the inflammatory response is not to increase heat. The overall goal of the inflammatory response is to destroy foreign cells or bacteria.
Hence, the option (b) increase heat at the site of infection is incorrect.
Antibodies function in specific immune response. Antibodies target specific type of foreign cells or bacteria. The inflammatory response is an innate immune response. The inflammatory response does not target any specific bacteria.
Hence, the option (c) produce antibodies that bind and eliminate invading cells is incorrect.
Increasing blood flow to the site of injury would result in more blood loss. The body strives to conserve blood. Hence, platelets secrete proteins. These proteins form a blockage at the injured site. As a result, blood loss is prevented. In addition, proteins prevent more foreign cells from entering the body. Thus, the inflammatory response does not promote more blood flow to the injured site.
Hence, the option (d) increase blood flow is incorrect.

Question 3

What is the difference between an epitope and an antigen?

Answer 3

An antigen is any organic molecule that is capable of binding immune receptors or can trigger immune response. Antigens are generally large biomolecules. For example, the peptidoglycan, lipopolysaccharide, the coat proteins of virus, the toxins of bacteria, are all examples of an antigen.
An epitope is a small region of the antigen that actually binds to the immune receptors. For example, an antibody generated against an antigen actually binds only to a small portion of the antigen. This region is called an epitope. An antigen can have several epitopes; an antigen can have several different types of epitopes. Each epitope binds to a region on the immunoglobulin called the paratope.

Question 4

What is one of the differences between CD4 + and CD8 + T cells?

A) CD4 + cells are immature and CD8 + cells are mature.
B) CD4 + cells are activated and CD8 + cells are not.
C) CD4 + cells interact with class II MHC proteins, and CD8 + cells interact with class I MHC proteins.
D) CD4 + cells activate cell-mediated responses, and CD8 + cells activate humoral responses.