title: Anti-interleukin 6 receptor antibodies attenuate antibody recall responses in a mouse model of allosensitization.
abstract: BACKGROUND
  Interleukin (IL)-6 is a regulatory cytokine for T helper type 17 (Th17) and Treg cells and a potent stimulus for B/plasma cells. The current study evaluated the effect of IL-6 receptor (IL-6R) blockade with an antiYIL-6R monoclonal (mMR16-1) in alloantibody recall responses.
  
  
  METHODS
  A mouse model of human leukocyte antigen (HLA).A2 sensitization was used for studies to evaluate the efficacy of antiYIL-6R on alloantibody recall responses and to examine the impact of IL-6R blockade on Th17, Treg, follicular T helper (Tfh) and plasma cells using multiparameter flow cytometry, flow antibody binding, and enzyme-linked immunospot (ELISpot) assay.
  
  
  RESULTS
  Re-exposure of C57BL/6 mice to HLA.A2(+) skin allografts resulted in a surge of donor-specific (antiYHLA.A2) immunoglobulin (Ig)G antibodies. AntiYIL-6R treatment significantly decreased but did not eliminate alloantibody responses (IgG mean fluorescence intensity, 486 T 153 vs. control 792 T 193, P = 0.0076). Flow cytometry analysis showed that antiYIL-6R treatment resulted in reduction of IL-21+CD4+ (Th17) cells (P = 0.006 vs. control) and CXCR5(+)CD4(+) Tfh cells (P = 0.04), but increased foxp3(+)CD4(+) (Treg) cells in the CD4(+) population (P =0.04 vs. control). The IgG ELISpot experiments showed a significant reduction of IgG spots in the bone marrow and the spleen cells from the antiYIL-6RYtreated mice. In vitro treatment of mouse hybridoma (PA2.1) cultures with antiYIL-6R decreased IgG spot formation but had limited effect on cell proliferation.
  
  
  CONCLUSIONS
  The data indicate that antiYIL-6R therapy attenuates alloantibody recall responses by modulating a number of immune regulatory and effector cells, including Th17, Tfh, Treg, and importantly, the long-lived plasma cells in the bone marrow.
authors.affiliation: 1 Comprehensive Transplant Center at Cedars-Sinai Medical Center, Los Angeles, CA 2 Address correspondence to: Gordon Wu, M.D., Comprehensive Transplant Center, Cedars-Sinai Medical Center, 8900 Beverly Blvd. Los Angeles, CA 90048.
authors.forename: Irene
authors.initials: I
authors.lastname: Kim
authors.forename: Gordon
authors.initials: G
authors.lastname: Wu
authors.forename: Ning-ning
authors.initials: NN
authors.lastname: Chai
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Klein
authors.forename: Stanley
authors.initials: S
authors.lastname: Jordan
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001854:Bone Marrow Cells / Q000166:cytology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D002454:Cell Differentiation; D049109:Cell Proliferation; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D015789:HLA-A2 Antigen / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D020381:Interleukin-17 / Q000276:immunology; D007518:Isoantibodies / Q000276:immunology*; D008214:Lymphocytes / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D054380:Receptors, CXCR5 / Q000378:metabolism; D019947:Receptors, Interleukin-6 / Q000037:antagonists & inhibitors / Q000276:immunology*; D013154:Spleen / Q000166:cytology; D014184:Transplantation, Homologous
chemical_list: D000911:Antibodies, Monoclonal; C095085:CXCR5 protein, human; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D015789:HLA-A2 Antigen; D007074:Immunoglobulin G; D020381:Interleukin-17; D007518:Isoantibodies; D054380:Receptors, CXCR5; D019947:Receptors, Interleukin-6