Fig. 4. TrkA deficiency in the immune system causes increased Ig production. (A) T1-Cre;TrkA^neo/neo mice have increased levels of specific classes of Igs. IgM, IgG2a, IgG2b, IgG1 and IgG3 serum levels were measured by ELISA in 12-16-week-old mutants (KO, n=18) and control littermates (CTR, n=14). Data are expressed in Units/ml where 1 U=1 mg for IgM and 1 U=1 µg for IgG2a, IgG2b, IgG1 and IgG3. Bars: means±s.e.m. Data were evaluated using a two-tailed Student's t-test. ^*P<0.05. (B) C57Bl/6-SCID mice reconstituted with TrkA-deficient fetal liver cells (KO, n=10) have increased levels of serum Igs compared with TrkA wild-type-reconstituted controls (WT, n=6). C57Bl/6-SCID mice were reconstituted and monitored for Ig serum levels from 1 to 5 months after reconstitution. Data after two months from reconstitution are shown. All Ig classes are higher in TrkA-deficient animals, although only IgM and IgG2b are statistically different from controls (two-tailed Student's t-test. ^*P<0.05).