Several data suggest that immature lymphoid cells are more prone to pe
netration and therefore are affected more by antibodies than their mat
ure counterparts. In this study, we examined the penetration of monocl
onal anti-DNA antibodies in several models of immature cells. Results
confirm that most anti-DNA antibodies penetrate larger proportions of
immature cells than normal adult cells. It was also proven that anti-D
NA antibodies induce larger fractions of immature cells to undergo apo
ptosis than mature cells; however, there is not a numerical associatio
n between penetration and apoptosis. Additionally, the penetration and
induction of apoptosis of several anti-DNA monoclonal antibodies into
U937 and NIH-3T3 cells followed a rather heterogeneous pattern. When
mature and immature cells were stimulated polyclonally, it was shown t
hat polyreactive antibodies might act as an accessory signal to induce
apoptosis in immature cells. This process could contribute to the edi
tion of the immune repertoire. We propose that naturally occurring pol
yreactive antinuclear antibodies, through penetration and deletion of
self-reacting cells, could participate, either as a unique or secondar
y signal, in the mechanism of self tolerance. If these polyreactive an
tibodies undergo affinity maturation, it is possible they may develop
into pathogenic antibodies. (C) 1998 Academic Press