The nylon wool adherence marker of the B cell lineage appears at the resting pre‐B cell stage

The proliferative state of functionally defined populations of size‐separated pre‐B cells was investigated. The results presented here support the hypothesis that pre‐B cells are in the G2 phase when stable membrane IgM is first expressed. Small resting precursor cells significantly adhere to nylon wool columns, unlike larger cycling cells which can be enriched in the nonadherent fraction. These results suggest that the nylon wool “receptor” is a useful early B cell marker. Since the in vitro recruitment of both cycling and resting precursors was shown to be essentially dependent on agar mitogen(s), cumulative data suggest that the receptors for agar mitogen(s) appear shortly before surface IgM on proliferating pre‐B cells. Nylon wool adherence potential develops next on their resting progeny, followed by full lipopolysaccharide reactivity as cells further mature.