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Allelic Exclusion of B-Cells and Additional Antibody Diversity – Lymphocyte Development

by Peter Delves, PhD
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    So, why don’t we look at the numbers that are involved here; give us an idea about how incredible this mechanism is. There are less than 200 genes involved, yet those genes can encode millions of different antibodies. So we’ve already heard that around about 40 Variable gene segments for the immunoglobulin heavy chain, 27 Diversity gene segments and half a dozen or so Joining gene segments. And we’ve heard that this recombination is a random process. So a given B-cell can pick any one out of the 40, any one out of the 27, any one out of the six for the V, D and J. So because any of those can be picked, you can multiply those three numbers by each other. 40 x 27 x 6. So that gives us nearly six and a half thousand different possible sequences, protein sequences. From, what have we got there? 40 plus 27, that’s 67, plus 6. 73 if my maths is right. Okay, so a very small number of genes producing thousands of different protein sequences. And for the kappa (k) light chain, 40 Variable gene segments, any of which, any one of which can be chosen. No D remember, in the light chain. But five J. So we can multiply 40 by 5, that gives us 200. That’s quite a simple sum to do, and in a given B-cell, it may make exactly the same heavy chain rearrangement as another B-cell, but a different light chain. So we can actually take those two numbers and multiply them together. 6480 x 200, as I’m sure you all already worked out by mental arithmetic is 1.3 x 10^6; 1.3 million different protein sequences from that, way under 200 different gene segments. And of course there’s also the lambda (λ) light...

    About the Lecture

    The lecture Allelic Exclusion of B-Cells and Additional Antibody Diversity – Lymphocyte Development by Peter Delves, PhD is from the course Adaptive Immune System. It contains the following chapters:

    • Allelic Exclusion
    • How Many Different Antibodies are Possible?
    • Overview of the Additional Variability of Immunoglobulin Genes

    Included Quiz Questions

    1. 200
    2. 6,480
    3. 150
    4. 40
    5. 1,000
    1. Splice site mismatching
    2. Recombination
    3. Somatic hypermutation
    4. N-nucleotide addition
    5. Diversity in both the heavy and light chains
    1. TdT
    2. IgH
    3. Kappa light chain segments
    4. Lamda light chain segments
    5. Recombinatorial inaccuracies

    Author of lecture Allelic Exclusion of B-Cells and Additional Antibody Diversity – Lymphocyte Development

     Peter Delves, PhD

    Peter Delves, PhD


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