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Platelet depletion by anti-CD41 (αIIb) mAb injection early but not late in the course of disease protects against Plasmodium berghei pathogenesis by altering the levels of pathogenic cytokines

Henri C. van der Heyde, Irene Gramaglia, Guang Sun and Catherine Woods

Article Figures & Data

Figures

  • Figure 1.

    Mice treated early during P berghei infection with 0.1 mg of either anti-CD41 mAb or anti-CD61 mAb are protected from severe P berghei malaria despite no detectable effects of the mAb treatment on parasitemia. The cumulative survival (A, C) and average P berghei parasitemia plus or minus standard deviation (SD) (B, D) in groups of 10 mice injected intraperitoneally on day 1 with 0.1 mg of either anti-CD41 mAb (A, B) or anti-CD61 mAb (C, D). • indicates anti-CD41 day 1; ▴, anti-CD61 day 1; ♦, rat IgG day 1; ▪, PBS day 1.

  • Figure 2.

    Both anti-CD41 mAb and anti-CD61 mAb deplete platelets from the circulation. Blood (2 μL) was obtained from mice treated with either anti-CD41 mAb on day 1 of P berghei infection or PBS (A), and the average number plus or minus SD of cells is shown on the x-axis. A similar analysis was performed with blood from mice injected with anti-CD61 mAb on day 1 of infection (B). The blood was analyzed by flow cytometry for levels of CD41 and CD61 on the surface of platelets in the groups of mice indicated on the y-axis. A platelet region was defined based on the distinct forward and side scatter of platelets and the number of cells with different expression patterns of CD41 and CD61 were calculated by using counting beads. ▪ indicates CD41+CD61+; ▨, CD41CD61. Few (< 0.1%) if any single positive cells (CD41+CD61 or CD41CD61+) were detected.

  • Figure 3.

    Mice treated late with 0.1 mg of anti-CD41 mAb during P berghei infection are not protected from severe P berghei malaria, whereas early anti-CD41 mAb treatment does protect. The cumulative survival (A) and average P berghei parasitemia ± SD (B) in groups of 10 mice injected intraperitoneally on day 1 with 0.1 mg anti-CD41 mAb on day 1, 4, 5, or 6 of infection. • indicates anti-CD41 day 1; ▴, anti-CD41 day 4; ▾, anti-CD41 day 5; ♦, anti-CD41 day 6; ▪, PBS day 4.

  • Figure 4.

    Late depletion of platelets with anti-CD41 mAb injection does not protect against the development of severe malaria, whereas early treatment does. Blood (2 μL) was obtained from groups of mice injected with anti-CD41 mAb on either day 4, 5, or 6 of infection (not protected), from a group of mice injected with anti-CD41 mAb on day 1 (protected), and from a group of mice injected with PBS on day 4 (unprotected control). The number of CD41+CD61+ and CD41CD61 platelets were determined by flow cytometry. The average number plus or minus SD of cells is shown (x axis). ▪ indicates CD41+CD61+; ▨, CD41CD61. Few (< 0.1%) if any single positive cells (CD41+CD61 or CD41CD61+) were detected.

  • Figure 5.

    CD41CD61, PI events in the anti-CD41 mAb–treated mice label with vital dye fluorescein diacetate. Blood cells were analyzed by flow cytometry for their expression of CD41 and CD61 (platelet) and then were fluorescence-labeled with the vital dye fluorescein diacetate. (A) Blood cell labeling prior to addition of fluorescein diacetate. (B) Blood cell labeling after 10 minutes of incubation with fluorescein diacetate. The CD41CD61, PI cells are magenta and those cells labeling with fluorescein diacetate are green. The gray events comprise all cells that are not CD41CD61,PI cells. The inset % is the percentage of CD41CD61,PI cells that are labeled with fluorescein diacetate.

  • Figure 6.

    CD41 cells are of erythrocyte origin. Blood cells were analyzed by flow cytometry for their expression of CD41 (platelet) and Ter119 (erythrocyte) in uninfected mice (A, B) and in mice on day 6 of P berghei infection (C, D). The platelet set was defined by its forward scatter and side scatter (orange region in A, C) and microparticles and cell debris were excluded from the analysis (black set). The platelet subsets were color-coded in B and D based on their expression of CD41 and Ter119: the CD41+Ter119 platelet subset is purple, the CD41Ter119+ subset is red, the CD41Ter119 is green, and the CD41Ter199+ subset is blue. Note the colors identify the same platelet subsets in A and C. There were few orange events because virtually all cells within the platelet set were defined within the subsets.

Tables

  • Table 1.

    Detailed flow cytometric analysis of platelets in blood of mice during the course of P berghei malaria

    P
    Day 0Day 4Day 6Day 0 vs day 4Day 0 vs day 6
    % CD41+ cells forming intact RBC conjugates 8.6 ± 2.5 10.0 ± 2.4 36.0 ± 5.0 .7 < .0001
    % CD41+ cells forming microparticles 8.8 ± 1.0 6.2 ± 0.9 3.2 ± 0.9 < .0001 < .0001
    % CD41+ cells in platelet region 81 ± 2 82 ± 2 57 ± 5 .9 < .0001
    % microparticles that are CD41+ 31.2 ± 14.2 18.1 ± 10.2 0.4 ± 0.2 .1 .0002
    % microparticles that are Ter119+ 55.0 ± 16.8 56.2 ± 7.4 89.1 ± 1.8 .99 .0003
    No. CD41+ cells 848 136 ± 475 698 264 841 ± 173 789 20 191 ± 3 593 .03 .002
    No. CD41+ microparticles 72 953 ± 39 499 16 472 ± 11 438 617 ± 82 .009 .0009
    No. CD41+ cells in platelet region 683 532 ± 372 774 219 228 ± 145 295 11 645 ± 3 231 .02 .001
    No. CD41+ platelet: intact RBC conjugates 79 851 ± 62 859 24 643 ± 16 642 7 157 ± 689 .1 .04
    • The percentages of CD41+ cells plus or minus SD forming platelet microparticles, intact platelets, and platelet-erythrocyte conjugates are provided, as is an analysis of microparticles and the number plus or minus SD of platelet microparticles, intact platelets, and platelet-erythrocyte conjugates. The day-0 values comprise all the uninfected animals (n = 20) and n = 5 for analysis on day 4 and day 6 of infection. RBC indicates red blood cell.

  • Table 2.

    Analysis of selected cytokines and coagulation factors in groups of mice (n = 5)

    Cytokine/coagulation factorUninfectedRat IgG, day 4Anti-CD41, day 4P, rat IgG vs α-CD41
    IL-10, pg/mL 135 ± 10 166 ± 26 386 ± 72 .005
    IL-2, pg/mL 1 ± 1 30 ± 8 5 ± 3 .002
    IL-1α, pg/mL 29 ± 4 53 ± 12 110 ± 27 .03
    IFN-γ, pg/mL 1 ± 1 25 ± 15 84 ± 18 .01
    TNF-α, pg/mL 0 ± 0 7 ± 7 62 ± 19 .01
    IL-6, pg/mL 0 ± 0 3 ± 3 33 ± 9 .003
    Fibrinogen, μg/mL 3156 ± 339 3363 ± 147 4560 ± 337 .03
    fVII, ng/mL 0.70 ± 0.05 0.60 ± 0.05 0.64 ± 0.06 .6
    Tissue factor, ng/mL 3.1 ± 0.06 3.3 ± 0.2 3.0 ± 0.2 .5
    VWF, ng/mL 444 ± 48 348 ± 152 344 ± 92 .98
    • Plasma was obtained from uninfected mice or on day 4 of P berghei infection after injection with either anti-CD41 mAb or rat IgG on day 1 of P berghei infection. Mean plus or minus the standard error (SE) is reported. P indicates statistical significance by ANOVA for anti-CD41 mAb-treated group and rat IgG-injected group.