Periapical granuloma is mainly composed of:

The apical periodontal cyst is histologically identical with the periapical granuloma, from which it is actually derived, except for the presence of the epithelium-lined lumen.  The lesion is predominantly composed of plasma cells that are mixed with macrophages and lymphocytes with endothelial cells and fibroblasts. Periapical granuloma is not a true granuloma due to the fact that it does not contain granulomatous inflammation; however, periapical granuloma is a common term used. Reference: Shafer’s Textbook of ORAL PATHOLOGY Eighth Edition page no 78