Table 1.

Frequency and range of mutations in a 500-bp-long region in the intron downstream of the rearranged V_HD_HJ_H4 joints of GC B cells derived from pairs of M17^+/+ and M17^–/– mice

Organ and genotype	No. clones	No. mutated clones	Range, mutations/clone	No. mutations/no. bp (%)
Spleen
M17+/+	35	25	1-14	102/12 248 (0.83)
M17-/-	56	31	1-12	117/15 500 (0.75)
Peyer patches
M17+/+	26	25	1-20	196/12 500 (1.57)
M17-/-	30	25	1-25	213/12 447 (1.71)

Naive M17-/- B cells had a 0.03% mutation frequency.

GC B cells were isolated 14 days after immunization with NP-CG. Following cell lysis, a 600-bp fragment was PCR amplified from 40 000 cell equivalents using a primer pair that anneals in the framework 3 region of most J558 V genes and in the intron downstream of J_H4 gene segment.