Fig 1: Pathogenic C. albicans infection triggered platelet activation and CD40L release.(A and B) Quantification of platelets’ activation in 8 different groups of mice via CD62p surface expression analyzed by flow cytometry. A representative dot plot (A) and statistical chart of activated platelets (B) are shown. (C) Platelet activation upon in vitro co-culture of platelets with C. albicans. CD62p expression (left) and GPIIbIIIa expression (right) on platelet surfaces were analyzed by flow cytometry upon in vitro co-culture of platelets (1 × 107/sample) with different doses of C. albicans (1 × 105, 1 × 106 and 1 × 107/sample) in the presence of Gly-Pro-Arg-Pro (Pefa 6003) to prevent platelet aggregation. (D) Soluble CD40L levels in plasma of 8 groups of mice on day 7 after infection. (E) Soluble CD40L levels in plasma of patients with FXIII deficiency and in healthy control donors. (F) CD40L release in the platelet-C. albicans co-culture supernatant. Data are shown as mean ± SD; 1-way ANOVA was used for statistical analysis. **P < 0.01, ***P < 0.001. FSC-A, forward scatter area; PLA, proximity ligation assay; APC-A, allophycocyanin area.
Fig 2: Pathogenic C. albicans infection–promoted autoantibody production was mediated by platelet-released CD40L.(A) Binding of CD40L to B cells analyzed by flow cytometry. (B) Co-localization CD40L and CD40 on the surface of B cells. Memory B cells isolated from P1 (1 × 106/sample) were incubated with the platelet–C. albicans culture supernatant. Co-localization of CD40L and CD40 was examined by confocal microscopy. Representative images (out of 3) are shown. Scale bar: 10 μm. (C) Combined autoantibody release detected by ELISA. (D) Specificity of released autoantibody against C3 analyzed by ELISA. (E) Specificity of released autoantibody against FXIII analyzed by Far Western blot. (F) Neutralization of CD40L blocked autoantibody release by memory B cells. (C–F) CD40L-containing supernatant was added to the isolated memory B cells in the presence or absence of anti-CD40L. Purified CD40L was used as a positive control. Data are shown as mean ± SD; 1-way ANOVA was used for statistical analysis. ***P < 0.001. NC, negative control; PC, positive control; HB, memory B cells isolated from healthy donors; PB, memory B cells isolated from patient 1.
Fig 3: A model of action about the self-enhanced amplification loop of combined FXIII-C3 autoantibody generation for autoimmune FXIII deficiency.A combined FXIII-C3 autoantibody was identified in patients with autoimmune FXIII deficiency. The combined autoantibody, by forming a complex with C3, blocks C3 cleavage by C3 convertase, thereby inhibiting complement activation and complement mediated T cell activation, which increases host susceptibility to pathogenic C. albicans infections. Uncontrolled exogenous infections, by triggering platelets’ activation and platelet-related CD40L release, further promote autoantibody generation, resulting in progressive consumption of FXIII and C3. This process likely forms a self-enhanced amplification loop for autoantibody generation and progressive consumption of FXIII and C3 antigens.
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