Fig. 4.

Chicken splenocytes were incubated in triplicate for 48 h with medium or IBV M41 (10⁵ and 10⁴ EID₅₀). After 48 h, culture supernatants were collected and half of the samples were incubated at 65 °C for 30 min. Supernatants were tested using a commercial ELISA for ChIFN-γ. Recombinant ChIFN-γ protein (10 ng/ml) with or without heat treatment was included as a control. Groups with different letters are significantly different (p < 0.05).