 The initial "koding" dose and the minimum level required for detection determine how long the presence of "kodecytes" in the circulation can be monitored.For red blood "kodecytes" reliable monitoring of the presence of the "kodecytes" for up to 3 days post intravenous administration has been demonstrated in small mammals.The spacer (S) of a FSL construct has been selected so as to have negligible cross-reactivity with serum antibodies so kodecytes can be used with undiluted serum.