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
Macrophages
Lymphocytes
Plasma cells
All of the above