Figure 1.
Platelets actively phagocytose, immunoproteolyze, and present exogenous antigens through MHC-I. (A) To determine if murine and human platelets are capable of internalization and proteolysis of exogenous antigens, isolated mouse platelets (day 4 after CLP) or human platelets (day 0 upon recruitment) were pulsed with DQ-OVA for 1 hour at 37°C. BODIPY signal indicates successful internalization and processing of the DQ-OVA, which can be detected by flow cytometry. (B) Representative flow plots demonstrating BODIPY signal in murine platelets labeled with CD41. A majority of platelets were positive for BODIPY after DQ-OVA pulse (but not when platelets were fixed), showing active antigen internalization and processing by platelets. (C) Platelets isolated from mice after sham or CLP-induced sepsis actively internalized and proteolyzed DQ-OVA (n = 8-14). Fixed platelets pulsed with DQ-OVA were used as negative control. (D) Human platelets from both healthy donors and patients with sepsis actively internalized and proteolyzed DQ-OVA (n = 6-8). (E) Platelets isolated from sham or CLP mice were pulsed with OVA in vitro for 6 hours, and the OVA antigen peptide–MHC-I complex (SIIN:H-2Kb) was detected. As the arrows demonstrate, we observed significantly increased SIIN:H-2Kb expression in OVA-pulsed platelets from CLP mice compared with sham mice, suggesting increased antigen cross-presentation by platelets during sepsis. Summarized percentages of SIIN:H-2Kb platelets are shown on the right. Platelets from CLP mice showed significantly increased antigen cross-presentation (n = 9-12). (F) Mice received OVA without adjuvant (3 mg per day) for 3 consecutive days, and on day 4, SIIN:H-2Kb expression on the surface of platelets was measured by flow cytometry (n = 4-5; representative of 3 independent experiments). (G) SIIN:H-2Kb expression on the surface of platelets after OVA pulse positively correlated with total H-2Kb expression (n = 4-5; representative of 3 independent experiments). One-way analysis of variance with Tukey post hoc analysis, unpaired Student t test, and simple linear regression test were used. ****P < .0001. MFI, mean fluorescence intensity; plts, platelets; WGA, wheat germ agglutinin.

Platelets actively phagocytose, immunoproteolyze, and present exogenous antigens through MHC-I. (A) To determine if murine and human platelets are capable of internalization and proteolysis of exogenous antigens, isolated mouse platelets (day 4 after CLP) or human platelets (day 0 upon recruitment) were pulsed with DQ-OVA for 1 hour at 37°C. BODIPY signal indicates successful internalization and processing of the DQ-OVA, which can be detected by flow cytometry. (B) Representative flow plots demonstrating BODIPY signal in murine platelets labeled with CD41. A majority of platelets were positive for BODIPY after DQ-OVA pulse (but not when platelets were fixed), showing active antigen internalization and processing by platelets. (C) Platelets isolated from mice after sham or CLP-induced sepsis actively internalized and proteolyzed DQ-OVA (n = 8-14). Fixed platelets pulsed with DQ-OVA were used as negative control. (D) Human platelets from both healthy donors and patients with sepsis actively internalized and proteolyzed DQ-OVA (n = 6-8). (E) Platelets isolated from sham or CLP mice were pulsed with OVA in vitro for 6 hours, and the OVA antigen peptide–MHC-I complex (SIIN:H-2Kb) was detected. As the arrows demonstrate, we observed significantly increased SIIN:H-2Kb expression in OVA-pulsed platelets from CLP mice compared with sham mice, suggesting increased antigen cross-presentation by platelets during sepsis. Summarized percentages of SIIN:H-2Kb platelets are shown on the right. Platelets from CLP mice showed significantly increased antigen cross-presentation (n = 9-12). (F) Mice received OVA without adjuvant (3 mg per day) for 3 consecutive days, and on day 4, SIIN:H-2Kb expression on the surface of platelets was measured by flow cytometry (n = 4-5; representative of 3 independent experiments). (G) SIIN:H-2Kb expression on the surface of platelets after OVA pulse positively correlated with total H-2Kb expression (n = 4-5; representative of 3 independent experiments). One-way analysis of variance with Tukey post hoc analysis, unpaired Student t test, and simple linear regression test were used. ****P < .0001. MFI, mean fluorescence intensity; plts, platelets; WGA, wheat germ agglutinin.

Close Modal
This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal