CD84-deficient mice display normal platelet count and size.

<p>(A) CD84 targeting strategy: This scheme illustrates the detection of wild-type and <i>Cd84^−/−</i> (targeted) alleles. Upon homologous recombination, the pWH9 cassette containing a neomycin resistance gene disrupts the <i>Cd84</i> gene. An external probe (EP) recognizes a sequence downstream of 3′ arm in intron 2. With the pWH9 cassette, a new <i>Bam</i>HI restriction site is introduced, enabling the determination of a wild-type and <i>Cd84^−/−</i> band by Southern blot analysis. (B) Analysis of CD84 expression in wild-type (<i>Cd84^+/+</i>) and <i>Cd84^−/−</i> platelets by Western blot. Expression of GPIIIa was used as loading control. (C) Peripheral platelet counts and (D) platelet volume of wild-type and <i>Cd84^−/−</i> mice measured with a blood cell counter. (E) Determination of the platelet life span in wild-type and <i>Cd84^−/−</i> mice. Mice were injected with a DyLight 488-conjugated anti-GPIX Ig derivate to label platelets <i>in vivo</i>. Results are % of fluorescently labeled platelets at the indicated days after injection as determined by flow cytometry. Values are mean ± SD of 5 mice per group.