Discussion:
Effect of antigen exposure on B cell response
This solution is an interpretation of an experiment that measures hapten-specific B cell response by limiting dilution assay. The explanation begins with a brief background on antigen-antibody response and the limiting dilution method to evaluate it. The effect of pre-exposure to hapten and the generation of hapten-specific B cells is detailed. The benefit of this pre-exposure on antibody response during re-exposure to hapten is the crux of the experiment in this solution. We also discuss the effects of interleukins under these experimental conditions.
Using in vitro limiting dilution, an immunologist measured the number of B cells responding to the hapten TNP under various conditions. He used LIMITING numbers of B cells from either untreated mice or mice that had been immunized with TNP-BSA six weeks previously. All cultures contained appropriate T helpers and APC's. Some of the cultures also contained anti-IL4 or anti-IL6 antibodies known to block the activity of the corresponding interleukin. The number of B cells required to achieve limiting dilution, as well as the number of TNP-responding B cells under each condition, are shown below.
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B cell donors
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# B cells required to achieve limiting dilution
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Antign added to culture
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Antibodies added to culture
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# TNP-responsive B cells per 106 B cells
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Unimmunized
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10,000
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NONE
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NONE
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0
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TNP-CGG
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NONE
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112
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TNP-CGG
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anti-IL4
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0
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TNP-CGG
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anti-IL6
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0
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|
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Immunized with TNP-BSA
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1,000
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NONE
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NONE
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0
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TNP-CGG
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NONE
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1007
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TNP-CGG
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anti-IL4
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0
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TNP-CGG
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anti-IL6
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1001
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Questions:
1. What can you conclude regarding the effect of the initial antigen encounter on the subsequent precursor frequency of TNP-specific B cells?
2. What can you further conclude about the role of IL-4 and IL-6 in primary and memory B cell responses?