Adaptive Immunity - Tutorial 3

Question 1

Describe the primary & secondary immune response

Answer 1

• Primary response - is the response of the immune system them first time it is exposed to a particular antigen
• Secondary response - is due to increased numbers of specific memory cells which are more easily stimulated to produce plasma cells which produce antibodies.

Question 2

The importance of the secondary response

Answer 2

Secondary immune response causes the many memory cells to rapidly produce new plasma cells and large numbers of antibodies within a few days. Processing memory cells and the capacity to produce a rapid secondary response means that a person is immune to that specific antigen

Question 3

Name the four classes of antibodies and give one example of the clinical significance for each (e.g. IgM, last a short time therefore presence of these indicates a very recent or current exposure to the antigen)

Answer 3

• IgG - can cross the placenta so foetus and new-born get some protection from mother, the longest-lasting of the antibodies in the blood
• IgA - Most common antibodies in secretions and on mucous membranes: found in mucus, saliva, tears, bind antigens before they invade tissues
• IgM - Lasts only a short time, first type to be produced when antigen is encountered

IgE - involved in allergic reactions, play a role in immunity to parasitic infections in gut

Question 4

Briefly describe the four functions of antibodies (four ways that antibodies work)

Answer 4

1. ENHANCE PHAGOCYTOSIS
   - Antibodies coat the microbe making it easier for the phagocyte to recognise and ingest the microbe
   - Especially important for bacteria with a slimy capsule
2. ACTIVATES COMPLEMENT - When the antibody connects to the antigen it changes shape exposing a section of the antibody where complement proteins can bind. Complement is activated
3. Neutralisation: Antibodies bind to and block the attachment sites on the microbe to STOP IT BINDING TO THE HOST CELL
4. AGGLUTINATION - into large complexes so reduces the number of infectious units phagocytes have to deal with

Question 5

Describe the role of major histocompatibility complex (MHC)

Answer 5

To prevent the immune system from attacking our own cells we have proteins on the surface of our cells which identify us as self.