Lymph Nodes Draining Infections Investigated by PET and Immunohistochemistry in a Juvenile Porcine Model.

BACKGROUND

[F]FDG and [C]methionine accumulate in lymph nodes draining -infected foci. The lymph nodes were characterized by weight, [C]methionine- and [F]FDG-positron emissions tomography (PET)/computed tomography (CT), and immunohistochemical (IHC)-staining.

METHODS

20 pigs inoculated with into the right femoral artery were PET/CT-scanned with [F]FDG, and nine of the pigs were additionally scanned with [C]methionine. Mammary, medial iliac, and popliteal lymph nodes from the left and right hind limbs were weighed. IHC-staining for calculations of area fractions of Ki-67, L1, and IL-8 positive cells was done in mammary and popliteal lymph nodes from the nine pigs.

RESULTS

The pigs developed one to six osteomyelitis foci. Some pigs developed contiguous infections of peri-osseous tissue and inoculation-site abscesses. Weights of mammary and medial iliac lymph nodes and their [F]FDG maximum Standardized Uptake Values (SUV) showed a significant increase in the inoculated limb compared to the left limb. Popliteal lymph node weight and their FDG uptake did not differ significantly between hind limbs. Area fractions of Ki-67 and IL-8 in the right mammary lymph nodes and SUV in the right popliteal lymph nodes were significantly increased compared with the left side.

CONCLUSION

The PET-tracers [F]FDG and [C]methionine, and the IHC- markers Ki-67 and IL-8, but not L1, showed increased values in lymph nodes draining soft tissues infected with . The increase in [C]methionine may indicate a more acute lymph node response, whereas an increase in [F]FDG may indicate a more chronic response.