Figure 2. Group V sPLA₂ protects from K/BxN serum-transfer arthritis.

(A) Arthritis response in group V sPLA₂-null and congenic control mice mice in a BALB/c group IIA null background. Mice were injected with 20 µl of K/BxN serum at day 0 and 2, and disease development was monitored for 13 days. (B) Histomorphometric quantification of arthritis severity in group V sPLA₂-null and congenic control mice at experimental day 13. N=15 mice/group. Data are mean ± SEM pooled from three independent experiments. P < 0.001 for (A). (C) Representative mid-saggital ankle sections from group V sPLA₂ null and group V sPLA₂-control mice. Upper and lower panels are 25X and 200X magnification respectively (lower panel). White arrows demarcate the hyperplastic synovial lining surrounding a large effusion (upper) while black and white arrowheads highight bone and cartilage erosions respectively. Note the increased leukocytic infiltration, synovial lining hyperplasia and pannus formation in group V sPLA₂-null mice (T, tibia; S, synovial space; C, calcaneus). Figures representative of findings in 15 mice/group.