Germinal Center – Lymphocyte Activation

by Peter Delves, PhD

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    00:01 Again, germinal centers can be produced in response to antigenic stimulation.

    00:07 And really the germinal center can be thought of as the power house of the adaptive immune response.

    00:14 It’s really where all the cells that are necessary to generate an adaptive immune response get together.

    00:19 So you’ll have B-cells, you’ll have T-cells, you’ll have dendritic cells, you’ll have follicular dendritic cells and so forth. And although there are these distinct zones as we’ve seen, T-cell areas and B-cell areas in the secondary lymphoid tissues, of course the B-cells and the T-cells are not entirely separated from each other.

    00:39 They actually need to get together because some of the cell interactions that are required, require molecules on the surface of T-cells to interact with molecules on the surface of B-cells.

    00:50 So clearly the cells have to come in to cell-cell contact.

    00:52 They can’t be entirely separated from each other.

    00:55 So here we see in the top left, a tissue section that is stained to clearly demarcate the outer region of the germinal center, the mantle zone.

    01:07 And within the germinal center itself, two zones that stain with different intensities - a light zone and a darker staining zone.

    01:16 And these are characteristic of the germinal center.

    01:21 Looking now at an immunofluorescent section, again we can see the outer mantle zone and then within the germinal center itself, the light zone and the dark zone.

    01:33 Looking at B-cell migration into the germinal center, B-cells within the rest of the secondary lymphoid tissue will get together with helper T-cells and generate these germinal center structures.

    01:49 What happens in the dark zone of the germinal center is that there is extensive proliferation, cell division of the B-cells.

    01:58 Within the light zone, there is somatic hypermutation, there is affinity maturation and there is isotype switching or class switching of the B-cells.

    02:10 And this requires interaction of the B-cells with so called follicular helper T-cells, TFH, which is a population of helper T-cells that are specialized to help the B-cells in the germinal center.

    02:27 Follicular dendritic cells will show antigen to the B-cell receptor on the surface of the B-cell.

    02:36 So the end result, is that there will be activation and fine tuning of the B-cell response, there will be differentiation of the B-cells into both memory B-cells and into plasma cells.

    02:51 And there will be the exit of high affinity antibody secreting B-cells and memory B-cells from the germinal center.

    About the Lecture

    The lecture Germinal Center – Lymphocyte Activation by Peter Delves, PhD is from the course Adaptive Immune System.

    Included Quiz Questions

    1. Sites of antibody affinity maturation that are induced during immune responses.
    2. Sites of T cell production and development
    3. Sites of B cell development from a pre-B cell to an immature B cell
    4. Sites of phagocytosis of pathogens by the proliferating macrophages
    5. Site of the innate immune response generation
    1. Proliferation, somatic hypermutation, improved affinity, differentiation
    2. Somatic hypermutation, proliferation, improved affinity, differentiation
    3. Improved affinity, differentiation, proliferation, somatic hypermutation
    4. Differentiation, improved affinity, proliferation, somatic hypermutation
    5. Differentiation, proliferation, improved affinity, somatic hypermutation

    Author of lecture Germinal Center – Lymphocyte Activation

     Peter Delves, PhD

    Peter Delves, PhD

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