The Pathology and Pathogenesis of Mycobacterium bovis Infection 125
small amount of AFB in stage I and II granulo-
mas, mostly within the cytoplasm of macro-
phages, epithelioid cells and MNGCs (Fig. 9.3),
and a higher number of bacteria within the
necrotic cores of stage III and IV granulomas.
The four types of granulomas have been
found in the lung and lymph nodes from natural
and experimentally infected cattle, showing no
remarkable differences in different tissues when
studying conventional H&E-stained slides. The
presence and quantification of granulomas of
different stages have been used as an important
tool to evaluate strain pathogenicity and vaccine
efficacy in cattle (Johnson et al., 2006; Dean
et al., 2014, 2015; Salguero et al., 2017).
Several studies have been carried out to
study in depth the cell composition of granulo-
mas in bovines infected by M. bovis. Different
techniques (e.g. immunohistochemistry [IHC]
or in situ hybridization [ISH]) have been used
to characterize and quantify the presence
of macrophages, lymphocytes and their
subpopulations within tissue sections (Liébana
et al., 2008; Aranday-Cortés et al., 2013; Palmer
et al., 2015, 2016; Salguero et al., 2017).
Immunohistochemical detection of CD68
has been used to characterize and locateFig. 9.2. (a) Stage I granuloma showing clustered epithelioid macrophages with some Langhans-type
multi-nucleated giant cells (MNGCs). (H&E, 200×) (b) Stage II granuloma with abundant epithelioid mac-
rophages, visible MNGCs and an incomplete fibrous capsule. (H&E, 100×) (c) Stage III granuloma show-
ing a complete fibrous capsule and central necrosis. (H&E, 40×) (d) Stage IV granuloma with a complete
fibrous encapsulation, extensive central necrosis and mineralization. (H&E, 40×)
Fig. 9.3. Acid-fast bacilli within the cytoplasm of
a MNGC. (Ziehl-Neelsen, 600×)