Bronchus-associated lymphoid tissue (BALT) is considered to play an important role for the local immune response of the lung. We have been studying the function of BALT in delayed-type hypersensitive reaction of the lung. Our previous report showed that BALT of rabbits was histologically divisible into four different areas: lymphoepitheliallayer (LE), dome area (DA), follicular area (FA), and parafollicular area (PFA), and that the structure of BALT changed in rabbits sensitized with heat-killed bacillus Calmette Guerin (BCG). In the present study we researched the distribution of imrnurloglobulin (Ig) (IgG, IgA, and IgM)- positive cells and T cells in the lungs and BALT in both normal rabbits and rabbits with pulmonary granulomas induced by primary and secondary intravenous sensitization with heat-killed BCG. We detected Ig positive cells by the direct immunoperoxidase technique, using horseradish peroxidase (HRP)-labeled anti rabbit IgG-, anti rabbit IgA-, and anti rabbit IgM-IgG antibody. Also we detected T cells by the indirect immunoper oxidase technique, using M-108monoclonal antibody specific for rabbit T cells.
The following results have been obtained.
1) In the normal rabbit-BALT the distribution of the cells was as follows: LE; This area was consisted mainly of IgG-positive cells, IgA-positive cells and T cells. IgMpositive cells were scarce. DA; IgG-positive cells, IgM-positive cells and T cells could be seen in this area. FA: A center of FA is distributed by a number of surfaces IgM-posltlve cells. A slight degree of infiltration of IgG-positive cells and T cells was found in this area. PFA; This area was consisted mainly of T cells. There were also a number of IgG-positive cells and IgA-positive cells and small number of IgM-positive cells.
2) In normal rabbits a nurnber of IgG-positive cells and IgA-positive cells were seen within bronchial walls, and a few of these cells were found in bronchiolar walls and alveolar septa. IgM-positive cells distributed sparsely in the bronchial walls. The number of the Ig-positive cells distributing in the bronchial walls was closely ralated to the degree of the development of BALT.
3) A marked in filtration of IgG-positive cells and IgA-positive cells was seen in the peripheral regions of the epithelioid cell granulomas from one day after the secondary BCG-sensitization, and then the number of these cells increased gradually. The number of the cells in the granulomas reached the peak three weeks after the sensitization, and subsequently decreased.
4) The number of sIgM-positive cells in FA markedly increased from four days after the secondary sensitization, and the findings could be recognized continuously for the subsequent five weeks.
The above results suggest that BALT may control the production of immunoglobulins of the lung, which may modify the delayed-type hypersensitive reaction in the lung.