There is little doubt that carbohydrates are crucial to the functions of NK cells. Exogenous carbohydrates alter the cytolytic capabilities of these cells, treatment of NK cells with glycosidases or inhibitors of glycosylation affect function, NK cells can bind selective sugars, and NK cells can be identified and subdivided into functionally distinct subsets on the basis of cell surface carbohydrates. Yet, despite the large number of observations which have been made concerning carbohydrates and NK cells, there is little consensus regarding these studies and few investigations which satisfactorily demonstrate specific mechanisms for the observed effect of the carbohydrates. Almost certainly, the number of diverse observations implies roles for carbohydrates in multiple areas of NK function, probably including target recognition, tissue distribution and post-binding events in the lytic cascade. Hopefully, these observations made to date will be viewed as exciting preliminary studies which will entice more sophisticated investigations designed to elucidate the precise roles of carbohydrates in the functions of NK cells.

Flow cytometric cell sorting is commonly used to obtain purified subpopulations of cells for use in in vitro and in vivo assays. This can be time-consuming if the subpopulations of interest represent very low percentages of the cell suspension under study. Often the desired subpopulations are identified by twocolor immunofluorescence staining. Generally, cell sorting is performed with a flow cytometer configured to trigger on light scatter signals, then sort windows are set based upon the signals from both fluorescent markers. We demonstrate that triggering the cytometer with the fluorescence signal from antibody staining common to both of the desired subpopulations, then sorting the subpopulations based upon staining of a second marker, substantially increases the speed of cell sorting vis-a-vis traditional methods. This is because undesired events are not analysed, allowing an increase in the throughput rate. While desired subpopulations of cells can be obtained by this method, undesired (i.e., nonstaining) cell "contaminants" increase and may require a second sort. The combined time for the initial enrichment sort and a second sort can be less than sorting once using standard methodology. Alternatively, the degree of contamination may be controlled by adjusting the concentration of the cell suspension and by the sample flow rate.