Aim: This study was performed to determine the histologic structure and localization of the alpha-naphthyl acetate esterase (ANAE)-and acid phosphatase (ACP-ase) positive lymphocytes in hemal nodes of Kyrgyzstan's mountain Yaks (Bos grinniens).

Materials and Methods: For this purpose, tissue samples from hemal nodes of six, 2–4 year-old-aged Kyrgyzstan's mountain Yaks were used. After processing, tissue sections were taken and stained with Crossmon's trichrome stain. In frozen sections, alpha-naphthyl acetate esterase (ANAE) and acid phosphatase (ACP-ase) were demonstrated.

Results: The results showed that the hemal nodes were surrounded by a highly thick connective tissue capsule involving smooth muscle fibers and had a very large sinus system compromised by subcapsular and deep sinuses filled with blood. Cortical and medullar regions were not definite. Lymphatic nodules and cords were observed in the deeper region of hemal nodes. ANAE- and ACP-ase positive lymphocytes localized especially in the margin of the lymphatic nodules and also interfollicular areas.

Conclusions: Yaks are very important animals for Krygyzstan economi as food source because they provide milk, milk products, meat, and meat products. Besides, yaks can survive and adaptable to the highly extreme ecological conditions such as high altitude, very low annual average temperature, short growing season for calf, and great seasonal variation in feed supply. So it is thought that extensive research regarding this species must be planned.