The present invention relates to a method for generating immunoglobulin sequences against cell-associated antigens, more particularly, antigens that are membrane-anchored. The invention also provides immunoglobulin sequences obtainable by the method of the invention. Specifically, the present invention relates to the generation of immunoglobulin sequences by use of DNA vaccination. More specifically, the present invention relates to generation of immunoglobulin sequences in camelids, preferably directed against cell-associated antigens, in particular antigens with multiple transmembrane spanning domains, including GPCRs and ion channels, by DNA vaccination. Furthermore, the present invention relates to said immunoglobulin sequences against cell-associated antigens, more particularly, antigens that are membrane-anchored, such as e.g. GPCRs and ion channels, more preferably ion channels.