A hypothesis such as this implies that it might be possible to detect  clonal expansions in healthy subjects. In fact, small numbers of apparently clonal B cells with B-CLL cell characteristics do exist in the blood of about 3.5% of disease-free individuals. An even higher proportion of such clones have been found in the blood of first-degree relatives of patients with B-CLL (as often  as 12%). Although such studies of the BCRs of B lymphocyte expansions in normal disease-free individuals are limited, they further support this hypothesis in that these expansions are not only monoclonal but also use some of the same genes commonly encoding the BCRs of B-CLL clones.