Question

1. List and describe at least 6 different ways in which genetic diversity in immunoglobulins arise.

2. Present a scenario of infection in which you can describe the differences in cellular activation, cytokines, etc. in T-Dependent and T Independent antigens scenarios.

3. Describe three ways in which complement acts to protect the host during infection. Identify specific molecules/ convertases and their contributions to the immune response.

Answer 1

Immunoglobulin diversity can occur in many ways.

Antibody response can be stimulated with any substance as all substances have a unique affinity,binding strength, and specificity.

There are separate genes for every immunoglobulin chaino. Cloning of the immunoglobulin genes can occur due to the DNA re-arrangement of the b-cells.

The variability occurs when gene segment encodes with V ,J,D segments or the addition of P and N nucleotides. Hypermutation also adds to the diversity of immunoglobulin.

The different in diversities occur when:

1) Immunoglobulin genes are arranged in antibody cells.

DNA that are produced from the b cells that produce antibodies,the V and C sequence are on the same DNA When taken from different germline DNA. This is also called as somatic arrangement.

2)V region gets formed by the recombination of separate gene segments.

A V- region can pair with more than one gene segment. Therefore, multiple encoding with gene segments lead to diversity among the immunoglobulins.

3) There are many V region segments

There are many copies of the gene segment in the germline DNA. Any gene segment that pairs with any V- region creates a diversity of V regions among the immunoglobulins

4) The gene segments are used in different combinations

All V segments are not if the same frequency. Not all heavy and light chain can pair with each other. when a heavy chain pairs with a light chain, the complex formed is forms a diversity.

5)When there is somatic hypermutation

For mutation to occur, enhancers are required. When there is a mutation in the V region, the new diversity shows double stranded breaks in the DNA of the b- cells.

6) Addding or removing the nucleotide at the junction of the gene segment

During the process of encoding,a random number of nucleotide gets added or removed from the gene segments. When they are paired with V-segment,it forms a diversity in the 3rd hypervariable region of the gene segment. Two loops get paired with V segment,the third one codes partially with D gene. It also leads to addition or removal of nucleotides.

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