Disruption of Tfh:B Cell Interactions Prevents Antibody-Mediated Rejection in a Kidney Transplant Model in Rats: Impact of Calcineurin Inhibitor Dose

Abstract

We aimed to investigate the mechanisms of humoral immune activation in ABMR using a MHC-mismatched rat kidney transplant model. We applied low dose cyclosporine A (loCNI) to allow donor-specific antibody (DSA) formation and rejection and high dose cyclosporine A (hiCNI) for non-rejection. DSA and leukocyte subsets were measured by flow cytometry. Germinal centers (GC), T follicular helper cells (Tfh), plasma cells and interleukin-21 (IL-21) expression were analyzed by immunofluorescence microscopy. Expression of important costimulatory molecules and cytokines was measured by qRT-PCR. Allograft rejection was evaluated by a nephropathologist. We found that DSA formation correlated with GC frequency and expansion, and that GC size was linked to the number of activated Tfh. In hiCNI, GC and activated Tfh were virtually absent, resulting in fewer plasma cells and no DSA or ABMR. Expression of B cell activating T cell cytokine IL-21 was substantially inhibited in hiCNI, but not in loCNI. In addition, hiCNI showed lower expression of ICOS ligand and IL-6, which stimulate Tfh differentiation and maintenance. Overall, Tfh:B cell crosstalk was controlled only by hiCNI treatment, preventing the development of DSA and ABMR. Additional strategies targeting Tfh:B cell interactions are needed for preventing alloantibody formation and ABMR.

Safety and biodistribution of exosomes derived from human induced pluripotent stem cells

“…Changes in cellular and humoral immunities were analyzed by an Acoustic Focusing Flow Cytometer (Invitrogen, United States) and microplate reader (Tecan). The antibodies used for flow cytometry were anti-CD3 (Invitrogen, 11-0030-82) (Steines et al, 2021), anti-CD4 (Invitrogen, 17-0040-80), anti-CD8 (Invitrogen, 12-0084-82) (Aiello et al, 2017). ELISA kits (Elabscience, IgA E-EL-R3015, IgM E-EL-R3016, and IgG E-EL-R0518c) (He et al, 2019) were used to detect immunoglobulins.…”

Helper T Cell (CD4+) Targeted Tacrolimus Delivery Mediates Precise Suppression of Allogeneic Humoral Immunity

“…In GC selection, Tfh cells are stimulated by mature B cells to form a positive feedback loop in cell number growth and survival signal strength. Thus, GC size correlates with the number of activated Tfh cells [ 12 ]. Spleen mass in the allograft group increased by more than three times, compared to the isograft group.…”

“…As one of the effectors of GC reaction, IL-21R overexpresses during humoral rejection in kidney transplantation (Figure S1), suggesting the vital role of Tfhs in ABMR. ABMR symptoms can be reduced by Tfh cell monitoring [10,11], clearance [10], and uncoupling of their interactions with B cells [12]. Preliminary results have also shown that splenectomy and splenic irradiation can be used as rescue therapies for refractory and severe ABMR [8,[13][14][15][16].…”

Preconditioned Mesenchymal Stromal Cells to Improve Allotransplantation Outcome

“…However, all studies discussed in this report only evaluated the effects of preconditioned MSCs without supplemented immunosuppressants. The commonly used immunosuppressants, such as cyclosporin (CsA), tacrolimus, rapamycin, and mycophenolate mofetil, have different impacts on the level or function of specific immune cell populations, such as Tregs [83,84], or the interactions between different types of immune cells [85]. On the other hand, CsA was shown to promote MSC survival and exerted additive immunomodulatory effects on MSCs in vivo [86], although rapamycin may affect MSC proliferation [87].…”