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Maturation of mononuclear phagocytes in the lungs of young calves--in vitro study
C F Batista1, M G Blagitz, B P Santos
1University of São Paulo, Faculty of Veterinary Medicine and Animal Science (FMVZ-USP), Department of Internal Medicine, Av. Prof. Dr. Orlando Marques de Paiva, 87 São Paulo/SP, Brazil. camilafb@usp.br
Insights
Calf lung immunity changes with age, impacting disease susceptibility. Alveolar macrophages show reduced phagocytosis but increased numbers after 45 days, indicating immune maturation without passive immunity influence.
Area of Science:
- Veterinary Immunology
- Calf Health
- Innate Immunity
Background:
- Calf respiratory diseases are a major concern.
- Understanding age-related immune system development is crucial for identifying disease susceptibility periods.
- The innate immune response in calves' lungs requires further investigation.
Purpose of the Study:
- To evaluate the innate immune system in calves during early life.
- To identify age-related variations in lung innate response mechanisms.
- To correlate immune function changes with susceptibility to respiratory diseases.
Main Methods:
- Monitoring nine healthy calves over three months with eight immunologic evaluations.
- Collecting bronchoalveolar lavage samples via bronchoscopy.
- Identifying alveolar macrophages by CD14 expression and assessing phagocytosis of Staphylococcus aureus and Escherichia coli.
Main Results:
- Functional alterations in CD14-positive phagocytes were observed.
- Phagocytic activity peaked in the third week and decreased from 45 days of life.
- From 45 days onward, more alveolar macrophages were involved in phagocytosis, despite reduced individual cell capacity.
Conclusions:
- Calf alveolar macrophages exhibit reduced phagocytic capacity but increased cell numbers after 45 days of life.
- This shift suggests the initiation of an active immune response independent of passive immunity.
- Calves under 90 days of age have not yet achieved stable local innate immune response maturation.
Abstract:
The influences of age in calves' immune system are described in their first phase of life. We hypothesized that variations that occur in the main mechanisms of lung innate response can help to identify periods of greater susceptibility to the respiratory diseases that affect calves in the first stage of their life. This study aimed to evaluate the innate immune system. Nine healthy calves were monitored for 3 mo and 8 immunologic evaluations were performed. Bronchoalveolar lavage samples were recovered by bronchoscopy. The alveolar macrophages in samples were identified by protein expression of cluster of differentiation 14 (CD14) and underwent functional evaluation of phagocytosis (Staphylococcus aureus stained with propidium iodide and Escherichia coli). Data was assessed by one-way ANOVA (unstacked and parametric) and the Mann-Whitney test (nonparametric). Functional alterations in CD14-positive phagocytes were observed, with punctual higher intensity of phagocytosis in the third week and its decrease starting at 45 d of life. A gradual increase in phagocytosis rate was observed starting at this date. It is concluded that from 45 d of life on, alveolar macrophages have less phagocytic capacity but more cells perform this function. We suggest that this occurs because lung macrophages of calves start to maintain their immune response without passive immunity influence. Until 90 d of life, calves did not achieve the stability to conclude the maturation of local innate immune response.
