Expression of complement receptors 1 (CR1/CD35) and 2 (CR2/CD21), and co-signaling molecule CD19 in cattle

Area of Science:

• Immunology
• Molecular Biology

Background:

• The C3d fragment of complement component C3 enhances B lymphocyte activation.
• This occurs via co-ligation of the B cell antigen receptor (BCR) and complement receptor 2 (CR2/CD21).

Purpose of the Study:

• To investigate the diversity of complement receptors in cattle.
• To determine the expression of CR1, CR2, and CD19 in bovine immune cells.

Main Methods:

• Reverse transcriptase polymerase chain reaction (RT-PCR) was used to analyze gene expression.
• Flow cytometry was used to detect protein expression on immune cells.

Main Results:

• Cattle possess four distinct complement receptors from the Cr2 gene via alternative splicing.
• Two major CR2 gene variants, homologous to murine CR1 and CR2, exist in long and short forms.
• CR1 and CR2 expression was found on IgM(+) cells in spleen and peripheral blood.
• CD19, a CR2 co-signaling molecule, is also expressed on these cells.

Conclusions:

• Cattle exhibit complex alternative splicing of the Cr2 gene, generating diverse complement receptors.
• These receptors, along with CD19, are expressed on B lymphocytes, suggesting a conserved role in immune responses.