Effect of Corynebacterium parvum on bone marrow macrophage colony production, peripheral blood leukocytes, and histologic changes of tissues in calves

Area of Science:

• Veterinary Immunology
• Immunology
• Cellular Biology

Background:

• Corynebacterium parvum is known to modulate the immune system.
• Understanding its effects in young animals is crucial for veterinary applications.
• Previous studies have focused on different administration routes or species.

Purpose of the Study:

• To investigate the immunological effects of intravenous Corynebacterium parvum in calves.
• To assess changes in hematological parameters and tissue immune cell distribution.
• To evaluate the impact on lymphoid organs following formalin-killed C. parvum administration.

Main Methods:

• Calves received intravenous injections of formalin-killed Corynebacterium parvum.
• Bone marrow macrophage colony formation assays were performed.
• Peripheral blood cell counts (monocytes, granulocytes, lymphocytes) were analyzed.
• Organ weights and histological examination of liver, lungs, spleen, lymph nodes, thymus, and lymphoid tissues were conducted.

Main Results:

• No significant increase in bone marrow macrophage colonies or peripheral blood immune cells was observed.
• Treated calves exhibited increased spleen weight.
• Macrophage infiltrations were noted in the liver, lungs, spleen, and lymph nodes.
• Lymphoid hyperplasia occurred in bronchial-associated lymphoid tissue, thymus, and lymph nodes.

Conclusions:

• Intravenous formalin-killed Corynebacterium parvum in calves does not induce significant hematological immune cell proliferation.
• The treatment leads to organ-specific immune cell redistribution and lymphoid tissue hyperplasia.
• Corynebacterium parvum elicits a localized immune response in calves rather than a systemic increase in circulating immune cells.