The invention relates to a system and method for obtaining a cellular fraction enriched with defined cells effective in promoting a defined cellular response from an in vivo cellular sample. The system is closable to the atmosphere, and includes a cell suspension collection tube containing gel and anticoagulant, adapted such that, when containing cell suspension and centrifuged after treatment the collection tube yields separation fractions, a first fraction comprising cellular fluid, a second fraction comprising gel layer, a third fraction comprising enriched cellular portion on top of the gel layer and a fourth fraction comprising a cell poor portion. The cell poor portion may be extracted and discarded prior to extracting the enriched cellular portion.