CCR5 cytometry on dendritic cells, probles with isotype control - (Jul/17/2006 )

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I'm determinig CCR5 ewxpression on human monocyte-derived dendritic cells by flow cytometry. I use a PE-conjugated monoclonal antibody and its IgG2a isotype-PE control.
My problems is that the isotype control is always higher than the sample, with no fluorescence but higher.
What can be the problem????

CCR5 is a pain to get your antibody attached to. Recently tried to control expression of CCR5 on some cell lines (two of which I know 100% sure expressed high levels of CCR5).

You might wanna try different anti-human clones, I used 2D7 without succes.

Any possibility to try RT-PCR to make sure your cells express CCR5?

I,ve done semiquantitative RT-PCR and they express CCR5.

The literature says that dendritic cells' CCR5 level expression at the membrane is low (and usually lower than mRNA)

I use 3A9 clone, I'll try to use a different clone