Histopathological Changes in lung of Rabbit after exposure to Allergic fungi

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INTRODUCTION
Primarily, infection results from inhalation of the airborne spores, which are small enough to reach the alveoli of the respiratory system.Most patients suffering from aspergillosis have an impaired immune system that is often evoked by leukemia, neutropenia or after prolonged treatment with steroids, such as solid organ transplantation patients (Ellis, 1999).The mortality rate of aspergillosis among these patients lies between 30 to 90% (Ellis, 1999;Latgé, 1999).The primary route of human infection is via the inhalation of these airborne spores,, followed by conidial deposition in the bronchioles or alveolar spaces.In healthy individuals, conidia that are not removed by mucociliary clearance encounter epithelial cells or alveolar macrophages, the primary resident phagocytes of the lung.Alveolar macrophages are primarily responsible for the phagocytosis and killing of A. fumigates conidia as well as the initiation of a proinflammatory response that recruits neutrophils (one type of polymorphonuclear cell (PMN) to the site of infection.Conidia that evade macrophage killing and germinate become the target of infiltrating neutrophils that are able to destroy hyphae (Denning, 1998).

MATERIALS AND METHODS Histopathological Studies: Animals
Only 28 intact and healthy adult male Albino rabbits are used aged 3-4 months; of 3 -3.2gm body weight.The rabbits obtained from the Voluntary College of Mosul University, and were kept in their ventilated wooden cages.The dimensions of the cages were (1.5x1.5x1.0 meter) and were cleaned on regular daily using detergent while the cage ground was sieved to allow elimination of urine and waste.

Maintenance of the experimental animals:
The 28 New Zealand male white rabbits were used to determine the pathogenic effects of fungi to lower respiratory tract, reared at an optimal room temperature ranged between 22-25°C at 60% -70% humidity.
Animals were fed on locally prepared diet which formulated from natural ingredients suitable for growing maintenance.

Experimental Design:
All groups were inoculated by inhalation using swab from fungi into nasal twice daily.
The total 28 rabbits were divided into 7 groups, each of 4 rabbits as follows: Group 1: Control animals without exposure.Group 2: Animals were exposured with A.
niger.Group 3: Animals were exposured with C.
albicans.Group 4: Animals were exposured with A.

Histopathological examination:
All rabbits were sacrificed 2 weeks after the treatment.Lungs were dissected out and organs were fixed inside plastic containers filled with 100 mL of 10% formalin.

Histological study Control animals
The cross sections taken from the lungs of control animals showed a healthy structure of alveoli, normal septa with normal form bronchioles (Fig. 1).

A. fumigatus
A section in the lung infected with A. fumigatus demonstrates damaged alveoli, blood congestion in the intercellular spaces and infiltration of WBC.Pneumocytes could be seen in the alveolar walls but the patches of the congested blood had filled the intercellular spaces obscuring the fibroblasts (Fig. 4)

A. niger
A cross section in lung of a rabbit infected with A. niger demonstrates a thickened alveoli wall with congested blood patches with accumulation of immune cells filling the intercellular spaces of the pulmonary tissue.There seem to be severe inflammatory cells infiltration in (Fig. 6).

A. flavus
Pulmonary tissues of rabbits infected with A. flavus had almost similar architecture of those infected with other fungi (Fig. 7).Tochigi, et al., (2009) reported the effects of an Aspergillus species (Aspergillus flavus) on the lung tissues as an acute hemorrhage in the septa due to destruction of blood vessels with a moderate to severe infiltration of mononuclear cells in the lungs.Similar results are found in the present results.The Aspergillus fumigatus had also caused an extensive infiltration of mononuclear cells to the pulmonary tissue mice (Murayama, et al., 2009).The effect of Aspergillusniger and Aspergillus flavus on the pulmonary tissues, had led to congestion and mild perivascular edema with thickening and hyalinization of the blood vessel walls in all animals while peri-bronchial and perivascular lymphocytic infiltration were detected in each individual animal (Jayabarathi and Mohamudha, 2010).Another study on birds demonstrated that Aspergillus species, particularly Aspergillus niger and Aspergillus flavus had led to infiltration of heterophils, lymphocytes and monocytes in the alveoli walls (Atkinson and Brojer, 1998).Results of these two studies are in agreement with this study.

C. albicans
Various lesions in pulmonary tissues i.e. thickening of alveoli walls with congestion of blood between the walls, mild inflammatory cells infiltration and accumulation of pneumocytes and lymphocytes appeared in most sections (Fig. 10).
An extensive interstitial pneumonic lesion characterize by thickening of alveolar walls due to congestion of alveolar capillaries and infiltration of mononuclear cells causing narrowing of alveolar lumen.Also there was a perbronchial lymphoid tissue hyperplasia and in advance cases a pulmonary fibrosis infected with Candida albicans were found in the pulmonary tissues in white mice (Inoue, et al., 2009;Al-Jeboori and Al-Harreery, 2013).Both studies are in agreement with the present study.

C. albicans
Various lesions in pulmonary tissues i.e. thickening of alveoli walls with congestion of blood between the walls, mild inflammatory cells infiltration and accumulation of pneumocytes and lymphocytes appeared in most sections (Fig. 11).
An extensive interstitial pneumonic lesion characterize by thickening of alveolar walls due to congestion of alveolar capillaries and infiltration of mononuclear cells causing narrowing of alveolar lumen.Also there was a perbronchial lymphoid tissue hyperplasia and in advance cases a pulmonary fibrosis infected with Candida albicans were found in the pulmonary tissues in white mice (Inoue, et al., 2009;Al-Jeboori and Al-Harreery, 2013).Both studies are in agreement with the present study.

Alternaria:
A cross section in lung of a rabbit infected with A. alternaria demonstrates a thickened alveoli wall with congested blood patches with immune cells filling the intercellular spaces of the pulmonary tissue.There seem to be severe inflammatory cells infiltration in (Figs. 12&13).The effect of Alternaria alternate on the lung tissues in white mice infected with Alternaria alternate had led to thickening of the septa and accumulation of infiltration mononuclear cells around the vessels and the bronchioles (Havaux, et al., 2005).This is again in an agreement with the results of the present study.In horse Alternaria lead to infiltration mononuclear cells in the alveoli walls and around the vessels and the bronchioles (Beech, 1975).These results are similar to the present study.

Fusarium
Considerable damage to the alveoli walls with congestion of blood between the walls were detectable in most sections of lungs infected with Fusarium.In addition, severe and clear inflammatory cells infiltration of lymphocytes and pneumocytes were visible between the cells of the septa with fibroblasts (Figs.14&15).
The effect of Fusarium kyushuense on lung tissues in white mice infected with F. kyushuense caused infiltration of plasma cells and lymphocytes in the alveoli walls Koichi, et al., (2000) while it led to infiltration of mononuclear cells in the alveoli walls and widening of interlobular septa of weaned piglets Dilkina, et al., (2000).Both studies are in agreement with the results of the present study.

It is concluded that:
Various histological changes appeared in the lung of rabbits.The Aspergillus fumigatus had caused an extensive infiltration of mononuclear cells to the pulmonary tissue rabbits.The effect of Aspergillus niger and Aspergillus flavus on the pulmonary tissues, had led to congestion and mild perivascular edema with thickening and hyalinization of the blood vessel walls in all animals while peri-bronchial and perivascular lymphocytic infiltration were detected in each individual animal.
The effect of Candida albicans on pulmonary tissues had led to thickening of alveoli walls with congestion of blood between the walls, mild inflammatory cells infiltration and accumulation of pneumocytes and lymphocytes appeared in most sections.Alternaria leads to infiltration mononuclear cells in the alveoli walls and around the vessels and the bronchioles.Fusarium caused damage to the alveoli walls with congestion of blood between the walls in most sections of lungs infected.In addition, severe and clear inflammatory cells infiltration of lymphocytes and pneumocytes were visible between the cells of the septa with fibroblasts.

ACKNOWLEDGMENT
I am grateful for all that support me throughout our research.

Fig. 1 :
Fig. 1: Histological Section in the normal lung shows A-normal structure of alveoli; B-the alveoli wall and normal lung tissue (H&E stain, 100x) .