The predominance of Κ over λ light chains (approximately 20:1) in serum Ig, myeloma proteins, and surface Ig (slg) on splenic B cells of adult mice is presumably a consequence of the greater number of subgroups and V region gene segments associated with Κ loci. However, the Κ:Λ ratio has been reported by several laboratories to be closer to unity in normal neonatal mice and in immunedefective CBA/N mice, using indirect immunofluorescent microscopic techniques. In order to examine these slgλ cells, we prepared directly fluoresceinated, affinity purified F(ab’)2 antibodies of defined fluorescein:protein (F: P) ratio and with specificity for the constant regions of λ or Κ light chains. The anti-A antibody was specific for all λ-containing myeloma proteins tested regardless of heavy chain-class association, but reacted with no Κ-containing myeloma proteins; the anti-Κ reagent had the opposite pattern of reactivity. Fluorescent staining with the anti-λ antibody on the fluorescence-activated cell sorter (FACS) was calibrated with the aid of several spontaneous B cell lymphomas in BALB/c mice that bore slg λ. λ-Specific staining could be blocked completely by preincubation of this antibody with λ- but not κ-containing myeloma proteins. Surface Igκ, λ, and µ were then examined on spleen cells of neonatal and maturing normal (CBA/N × BALB/c)F1 and (CBA/N × DBA/2)F1 female mice, and of abnormal F1 male mice of the 2 crosses. The frequency of slgλ cells was determined by subtracting from experimental FACS histograms either the low number of cells that appeared to stain positively with an irrelevant antibody of similar protein concentration and F:P ratio, or the number of cells that were stained after preincubation of the specific antiserum with inhibiting amounts of λ-containing myeloma proteins. The net frequency of slgλ cells determined with both assay procedures remained constant, at about 5% of total slg (Κ + λ) bearing cells, throughout neonatal development and maturation of normal and immune-defective CBA/N F1 mice.
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Kessler et al. (1981) studied this question.