|Bowden, Lacy - TEXAS A&M UNIVERSITY|
|Lowry, Virginia - TEXAS A&M UNIVERSITY|
Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 9, 1997
Publication Date: N/A
Interpretive Summary: Baby chicks are exposed to many microorganisms, such as Salmonella, during the first week after hatch. The chicks are highly susceptible to these infections because their immune system (the system that allows the chicks to fight off infections) has not fully developed. Heterophils are specific white blood cells whose primary functions are to eat and destroy foreign material, such as Salmonella, that may invade the chicks¿ system. The objective of this experiment was to determine whether heterophils during the first week after hatch could eat and kill Salmonella effeciently. Heterophils from baby chicks were found to eat and kill more salmonella after 4 days of life than during the first 3 days. These results are important to the poultry industry because they show that it takes the baby chick at least 4 days to develop an immune system.
Technical Abstract: Chicks are most susceptible to Salmonella infection during the first four days post-hatch. In poultry, one of the primary cells in the innate immune response to early bacterial invasion by Salmonella is the heterophil. Previous studies using a granulocytopenic chicken model in more mature birds demonstrated the significant role heterophils have in the defense mechanism against Salmonella. Studies in the past have also shown the efficiency of heterophils from 3- to 5-week-old chickens to phagocytose and kill Salmonella as compared to monocytes. During the present study, we investigated the phagocytic and bactericidal activities of heterophils from chickens during the first 7 days post-hatch to evaluate whether decreased heterophil function plays a role in the susceptibility of young chicks to Salmonella infections. The phagocytic index of the heterophil did not change on Day 1 or Day 4, but then doubled by Day 7 (Day 1, 30.69; Day 4, 33.99; Day 7, 60.46). Interestingly, the bactericidal activity of the heterophils from all three age groups efficiently killed Salmonella enteritidis. Based on this data, we conclude that a relationship exists between the age of the chick, the functional activity of the heterophil, and the susceptibility to organ invasion by Salmonella.