Figure 1.
CR1/2 on FDCs are required for a robust IgG anti-SRBC response to SRBC.
BALB/c and Cr2−/− mice were irradiated and reconstituted with either BALB/c or Cr2−/− bone marrow. Six weeks after reconstitution, mice (n = 6/group) were immunized i.v. with 5×106, 5×107, or 5×108 SRBC. All mice were bled at indicated time points. Sera were diluted 1∶125 (A) or 1∶625 (B and C) and screened for IgG anti-SRBC in ELISA. P-values represent comparisons between the responses in recipients with the same background; ns = p>0.05; * = p<0.05; ** = p<0.01; *** = p<0.001. Representative of two (A) or one (B, C) experiments.
Figure 2.
Wildtype and Cr2−/− B cells produce similar amounts of IgG anti-SRBC.
CB17 (Igb allotype) mice were irradiated and reconstituted with either BALB/c or Cr2−/− bone marrow (both Iga allotype) (n = 6/group). Six weeks after reconstitution, chimeras and Cr2−/− (n = 4, as negative control) mice were immunized with 5×107 (A and C) or 5×108 SRBC (B and D) i.v. All groups were bled at indicated time points. Sera were screened for total IgG anti-SRBC (A and B; diluted 1∶320) and for SRBC-specific IgG1 and IgG2a of the a and b allotype (C and D; diluted 1∶40). P-values represent comparisons between the responses in mice transplanted with BALB/c and Cr2−/− bone marrow; ns = p>0.05; * = p<0.05; ** = p<0.01; *** = p<0.001. Representative of one experiment.
Figure 3.
Wildtype and Cr2−/− B cells produce similar amounts of IgG anti-SRBC in the same mouse.
CB17 (Igb allotype) and Cr2−/− (Iga allotype) mice were irradiated and reconstituted with a mixture of CB17 and Cr2−/− bone marrow, resulting in mice having both CR1/2 positive and negative B cells but either expressing CR1/2 on FDCs (n = 6–8) or not (n = 6–8). Six weeks after transplantation, mice were immunized with 1×107 (A and D), 5×107 (B and E) or 5×108 (C and F) SRBC i.v. All groups were bled at indicated time points. Sera were diluted 1∶40 and screened for total IgG anti-SRBC (A–C) or for IgG1 and IgG2a of Iga and Igb allotypes (D–F). P-values were calculated with Student's t-test and represent comparisons between the responses in mice expressing CR1/2 on FDCs or not (Student's t-test; A–C), and between the different allotypes within the same mouse (paired Student's t-test, D–F), where ns = p>0.05; * = p<0.05; **, = p<0.01; ***, = p<0.001. Representative of three experiments.
Figure 4.
CR1/2 on B cells and FDCs is required for optimal antibody responses to IgM-SRBC complexes.
BALB/c and Cr2−/− mice were irradiated and reconstituted with either BALB/c or Cr2−/− bone marrow. Six weeks after transplantation, mice were immunized with 5×105 (A–D) or 5×106 (E–H) SRBC alone (open squares) or together with IgM anti-SRBC with a hemagglutination titer of 1∶32 (filled squares) or with IgM anti-SRBC alone (open triangles) (n = 6/group). All mice were bled at indicated time points. Sera were diluted 1∶25 (A–D) or 1∶625 (E–H) and screened for IgG anti-SRBC. Two statistical comparisons were made, both using Student's t-test. First, comparisons between the responses in mice immunized with SRBC alone versus IgM and SRBC (to determine whether IgM enhanced antibody responses significantly; filled versus open symbols), where ns = p>0.05; * = p<0.05; ** = p<0.01; *** = p<0.001. Second, comparisons between the responses between various chimeras immunized with IgM-SRBC (to determine whether CR1/2+ B cells contributed significantly to the antibody response to IgM-SRBC in mice with CR1/2+ FDCs (A vs B; E vs F) and CR1/2− FDCs (C vs D; G vs H)), where ns = p>0.05; ° = p<0.05; °° = p<0.01; °°° = p<0.001. For graphic clarity, non-significant differences are not indicated. Representative of one (A–D) and two (E–H) experiments.
Figure 5.
Antibody responses in chimeric mice after immunization with SRBC alone or IgM anti-SRBC+SRBC.