mTOR has distinct functions in generating versus sustaining humoral immunity
Derek D. Jones, … , Brendan M. Weiss, David Allman
Derek D. Jones, … , Brendan M. Weiss, David Allman
Published October 17, 2016
Citation Information: J Clin Invest. 2016;126(11):4250-4261. https://doi.org/10.1172/JCI86504.
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Research Article Immunology

mTOR has distinct functions in generating versus sustaining humoral immunity

Abstract

Little is known about the role of mTOR signaling in plasma cell differentiation and function. Furthermore, for reasons not understood, mTOR inhibition reverses antibody-associated disease in a murine model of systemic lupus erythematosus. Here, we have demonstrated that induced B lineage–specific deletion of the gene encoding RAPTOR, an essential signaling adaptor for rapamycin-sensitive mTOR complex 1 (mTORC1), abrogated the generation of antibody-secreting plasma cells in mice. Acute treatment with rapamycin recapitulated the effects of RAPTOR deficiency, and both strategies led to the ablation of newly formed plasma cells in the spleen and bone marrow while also obliterating preexisting germinal centers. Surprisingly, although perturbing mTOR activity caused a profound decline in serum antibodies that were specific for exogenous antigen or DNA, frequencies of long-lived bone marrow plasma cells were unaffected. Instead, mTORC1 inhibition led to decreased expression of immunoglobulin-binding protein (BiP) and other factors needed for robust protein synthesis. Consequently, blockade of antibody synthesis was rapidly reversed after termination of rapamycin treatment. We conclude that mTOR signaling plays critical but diverse roles in early and late phases of antibody responses and plasma cell differentiation.

Authors

Derek D. Jones, Brian T. Gaudette, Joel R. Wilmore, Irene Chernova, Alexandra Bortnick, Brendan M. Weiss, David Allman

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Figure 2

Primary and secondary antibody responses are arrested during mTORC1 inhibition.

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Primary and secondary antibody responses are arrested during mTORC1 inhi...
(A) Mice of the indicated genotypes were administered tamoxifen orally for 3 days, and the following day 106 CD19+ or CD19− cells were sorted for assessment of Raptor deletion by PCR. WT allele (+/+), 150 bp; floxed allele, 170 bp. The top image was overexposed to demonstrate efficient deletion of the floxed alleles in CD19+ cells in CD20-Tam-Cre–positive (Tam-Cre–positive) mice. Representative of 2 separate experiments using at least 3 mice per group. (B) Mice of the indicated genotypes were immunized with NP-CγG, and anti-NP IgG1 titers were determined by ELISA. On day 38 after immunization, mice were boosted with antigen, followed by 3 consecutive oral administrations of tamoxifen to induce Cre recombinase activity. Secondary responses were monitored on days 4, 7, 11, and 16 after boost. fl/fl Tam-Cre (n = 14), fl/+ Tam-Cre (n = 5), +/+ Tam-Cre (n = 3), fl/fl no Cre (n = 6), +/+ no Cre (n = 4). Representative of 2 independent experiments. Data represent mean ± SEM. *P < 0.01 as determined using a Kruskal-Wallis test with Dunn’s multiple comparison test. Asterisks indicate significance between fl/fl Tam-Cre mice and +/+ no Cre controls; no other pairwise comparisons reached significance. (C) Mice of the indicated genotypes (4 mice per group) were treated for 3 consecutive days with tamoxifen prior to immunization with NP-CγG, and NP-specific IgM titers were determined by ELISA. *P < 0.05 as determined using a Student’s t test. (D) B6 mice were immunized with NP-CγG, and anti-NP IgG1 titers were determined by ELISA. Mice were boosted on day 32 after immunization and treated with rapamycin (20 mg/kg) daily for the next 3 days. *P < 0.0001 as determined using a Student’s t test comparing control (n = 4) and rapamycin-treated (n = 4) mice. Representative of 2 independent experiments.