[Characterization of B1-cells during experimental leukomogenesis.]

Area of Science:

• Veterinary Immunology
• Virology
• Bovine Infectious Diseases

Background:

• Bovine leukemia virus (BLV) causes persistent lymphocytosis (PL) in cattle.
• PL involves polyclonal expansion of CD5+, IgM+ B lymphocytes.
• Early B cell dynamics in BLV infection remain unclear.

Purpose of the Study:

• Quantify IgM+ and CD5+ B cells during the immune response to BLV.
• Elucidate lymphocyte priming mechanisms in BLV infection.

Main Methods:

• Experimentally infected 8-month-old calves (n=8) with BLV; controls (n=3) received saline.
• Monitored B-lymphocyte populations (IgM+, CD5+) via immunoperoxidase staining.
• Blood samples collected on days 5, 7, 14, 21, 28, and 65 post-infection.

Main Results:

• CD5+ B cell levels increased by day 14, indicating polyclonal proliferation.
• BLV appears to target CD5+ B cells initially.
• Absence of surface IgM and CD5 aggregation on lymphocytes in infected cattle.

Conclusions:

• B1 cells are a primary target for BLV.
• IgM+ and CD5+ cells show functional differences early in infection.
• Increased CD5+ cells may involve T cells, not solely B cells.