B cells are not currently known to be capable of producing granzyme B or being cytotoxic. We recently found that human B cells activated with Interleukin 21 (IL-21) and antibodies to the B cell receptor (BCR) or immunostimulatory oligonucleotides (CpG ODN), can produce granzyme B. Further studies were done to assess the biological and potential therapeutic significance of this finding. Granzyme B ELISpot, intracellular staining for granzyme-B, quantitative real time RT-PCR for granzyme B messenger RNA and gene expression array confirmed B cells obtained from the peripheral blood of normal individuals (Fig. 1) and many B cell lines including Namalwa, Daudi, Ramos and EBV-transformed lymphoblasts, can be induced to produce granzyme B. This granzyme B is functional as demonstrated by cleavage of a granzyme B-sensitive colorimetric substrate. IL-21 based treatment also increased the transcription of the gene for perforin and the production of Interferon-γ in select B cell populations. We conclude that IL-21 based therapy can induce B cells to produce functional granzyme B and other components known to be present in the cytotoxic granules of CTL and NK cells. These unexpected findings could have significant implications on our understanding of the role of B cells in immune regulation and for a variety of immune phenomena including auto-, cancer and infectious immunity.

Figure 1.
Figure 1. Interleukin 21 (IL-21) induces de-novo synthesis of Granzyme B by activated B cells. Peripheral blood mononuclear cells (PBMC) were stimulated with the above depicted agents for 18 hours. After further incubtion with Brefeldin A for 4 hours cells were harvested, fixed, permeabilized, stained with PE- and PE-Cy5-labeled antibodies against Granzyme B and CD19, and analyzed flowcytometrically.
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Interleukin 21 (IL-21) induces de-novo synthesis of Granzyme B by activated B cells.Peripheral blood mononuclear cells (PBMC) were stimulated with the above depicted agents for 18 hours. After further incubtion with Brefeldin A for 4 hours cells were harvested, fixed, permeabilized, stained with PE- and PE-Cy5-labeled antibodies against Granzyme B and CD19, and analyzed flowcytometrically.

Figure 1.
Figure 1. Interleukin 21 (IL-21) induces de-novo synthesis of Granzyme B by activated B cells. Peripheral blood mononuclear cells (PBMC) were stimulated with the above depicted agents for 18 hours. After further incubtion with Brefeldin A for 4 hours cells were harvested, fixed, permeabilized, stained with PE- and PE-Cy5-labeled antibodies against Granzyme B and CD19, and analyzed flowcytometrically.
View largeDownload slide

Interleukin 21 (IL-21) induces de-novo synthesis of Granzyme B by activated B cells.Peripheral blood mononuclear cells (PBMC) were stimulated with the above depicted agents for 18 hours. After further incubtion with Brefeldin A for 4 hours cells were harvested, fixed, permeabilized, stained with PE- and PE-Cy5-labeled antibodies against Granzyme B and CD19, and analyzed flowcytometrically.

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Topics:
b-lymphocytes, granzyme b, interleukins, lymphocytes, granules, interleukin-21, antibodies, brefeldin a, cd19 antigens, cancer

Disclosure: No relevant conflicts of interest to declare.

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2006, The American Society of Hematology
2006
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