It depends on how many macrophages you need for your experiments, as ~10 mL of blood can give rise to around ~1x10^6 macrophages.  The general protocol for derivation of human macrophages is to isolate PBMC from blood, wash several times with PBS to remove platelets and then allow them to adhere to tissue culture treated dishes over the course of a few days. 

However, most protocols need optimisation depending on what you would like to do with the macrophages at the end of culture, and this determines whether you culture the macrophages in complete medium or in the presence of growth factors such as M-CSF.  Serum (no serum/FCS/autologous) also plays a big role in the number/survival/behaviour of the resulting macrophages too, as does the density at which you seed the PBMCs, since macrophages ideally like to form a contiguous layer.  The articles below may provide a useful starting point!

http://www.ncbi.nlm.nih.gov/pubmed/12969568

http://www.ncbi.nlm.nih.gov/pubmed/23255209

Good luck!

Dear Dominic,

You can certainly culture monocyte-derived macrophages from a smaller volume of blood. For example, I'm currently isolating PBMCs from 36 ml of blood per patient to culture monocyte-derived macrophages and to perform functional experiments on cytokine secretion, mRNA & protein expression etc. The amount of PBMCs (~10-20% monocytes) available per ml whole blood varies from donor to donor, but you can expect roughly 1 -1.5 x 10^6 PBMCs per ml whole blood. For differentiation of human monocyte-derived macrophages, we seed e.g. 1.2-1.5 x 10^6 PBMCs/24-well and 5-6 x 10^6 PBMCs/6-well. Depending on your planned experimental setup, you should be able to get a rough approximate of the required blood volumes.

Best regards,

Kristiina