Effect of the removal of the Harderian gland in 1-day-old chicks on immunity following IB vaccination.

After removal of the Harderian gland in 1-day-old chicks (Hx birds), protective immunity to infectious bronchitis virus (IBV) was decreased 3 weeks after vaccination with the H120 strain of IBV. Protective immunity was measured by challenge. The decreased protection was not reflected in the neutralisation indices of the Hx birds. In contrast, the mean neutralisation index was higher in the Hx birds than in the vaccinated controls. The role of the lachrymal gland in the development of immunity to IBV is discussed.