Avian Infectious Bronchitis in Specific-Pathogen-Free Chickens: Quantitation of Serum Immunoglobulins by Electroimmunoassay

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Abstract
Immunoglobulin (Ig) levels in serum of individual 6 wk old specific-pahtogen-free (SPF) chickens differed markedly. Quantitation by electroimmunoassay showed that the Ig[immunoglobulin]G level was low at 6 wk of age (1.3 .+-. 0.67 mg/ml), increased gradually with maturity and by 16-18 wk of age was 2.6 .+-. 1.5 mg/ml. IgM levels were less variable during the same observation period (6-18 wk, 2.4 .+-. 0.50-2.2 .+-. 0.86 mg/ml). IgA was high initially and decreased with age (6-18 wk, 0.74 .+-. 0.78-0.26 .+-. 0.06 mg/ml). Single intratracheal vaccination with a moderate dose of live avian infectious bronchitis virus (IBV) and subsequent challenge-exposure with live virus via the respiratory tract did not markedly affect Ig levels. Birds vaccinated parenterally 2 or 3 times with liver or killed IBV vaccines had a marked increase in serum IgG after similar challenge-exposure. IgA and IgM levels in vaccinated SPF birds approximated those in control SPF birds througout the experimental period.