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1.     MP;, A. D. M. F. S. E. L. V. M. C. (n.d.). Peripheral B cell maturation. II. heat-stable antigen(hi) splenic B cells are an immature developmental intermediate in the production of long-lived marrow-derived B cells. Journal of immunology (Baltimore, Md. : 1950). from https://pubmed.ncbi.nlm.nih.gov/8409411/ (Accessed: 19th June 2022)

2.     Levine, M. H. et al. A B-cell receptor-specific selection step governs immature to mature B cell differentiation. Proceedings of the National Academy of Sciences 97, 2743–2748 (2000). Retrieved June 19, 2022, from https://www.pnas.org/doi/full/10.1073/pnas.050552997

3.     Liao, X., Makris, M. & Luo, X. M. Fluorescence-activated cell sorting for purification of plasmacytoid dendritic cells from the mouse bone marrow. Journal of visualized experiments : JoVE (2016). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5226086/. (Accessed: 19th June 2022)

4.     Polymerase chain reaction (PCR) (article). Khan Academy Available at: https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/biotechnology/a/polymerase-chain-reaction-pcr. (Accessed: 19th June 2022)

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A significant implication of the experimental findings is that there might be a pre-selection between the environmental antigens and the B cell repertoire. Another implication is that survival of B cells from positive selections can lead to the formation of memory cells due to a ligand-receptor interaction⁷.

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A major source of error comes from the chain-pairing effects. Due to the nature that immature B cells are all high in IgM levels, biases will not be able to affect the subsequent repertoire shift². Thus, whether the selection is negative or positive remains unsolvable.

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Major findings from this study was proven to be consistent with existing studies which examined the importance of continued BCR expression in survival of mature B cells⁶. What was lacking in previous studies is the research on the specificity of the BCR. Role of BCR was further explained in this study.

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The hypothesis stating that the step determining the survival of immature B cells is selective was proved to be true by this set of experiments. Another major finding is that the selection is positive².

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As shown in Figure 3, there is no major difference in the repertoire between immature and mature B cells in the control group, suggesting that the process of interest could not be a stochastic one.

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As demonstrated by figure 3, there were differences between the repertoire between immature and mature B cells, data from the second line also proves the hypothesis the process is done selectively.

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As a significant difference was observed between the frequencies between immature and mature B cells by figure 2, data from the first line is consistent with BCR-specific selection².

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Figure from: 1.     Levine, M. H. et al. A B-cell receptor-specific selection step governs immature to mature B cell differentiation. Proceedings of the National Academy of Sciences 97, 2743–2748 (2000). Retrieved June 19, 2022, from https://www.pnas.org/doi/full/10.1073/pnas.050552997

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Figure from: 1.     Levine, M. H. et al. A B-cell receptor-specific selection step governs immature to mature B cell differentiation. Proceedings of the National Academy of Sciences 97, 2743–2748 (2000). Retrieved June 19, 2022, from https://www.pnas.org/doi/full/10.1073/pnas.050552997

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A step to quantitatively test hypothesis².

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A step to understand structure and properties⁵.

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A step in which PCR products were cloned and sequenced².

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A step to ensure that target DNA is sufficient to be analyzed⁴.

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A step used to purify cell populations based on flow cytometry³.

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Transgenic mice.

Image By Maggie Bartlett, NHGRI. - http://www.genome.gov/pressDisplay.cfm?photoID=5006, Public Domain, https://commons.wikimedia.org/w/index.php?curid=19805359

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The study is of great importance because it shows that positive selection plays a huge role in BCR repertoire, and it lays the foundation for the evidence showing the receptor-ligand interactions in the survival of lymphocytes².

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The experiment is conducted in order to find out if the cell loss is governed by a stochastic or selective process through comparing the differences in BCR repertoire between immature and mature B cells² in mice model. If the BCR repertoires show significant differences, the process will be proven to be selective. The authors made the hypothesis that the step determining the survival of immature B cell is selective.

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It is pointed out by existing studies that most peripheral immature conventional B cells bearing fraction E will not be able to make it to maturity¹. Whether the cell loss is caused by a stochastic step, or a selective step remains unknown.

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Student Name: Le Chen
Student Number: 1002640939
Infographic Assignment #4