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Microbes & Immunity Pulmonary immunity: Pathogens versus protectors

2.5. Descriptive themes sentinels, capturing antigens and migrating to lymph

The findings were organized into descriptive themes to nodes to initiate adaptive immune responses. Neutrophils,
highlight key insights: while typically associated with acute inflammation, are also
(i) Pathogen strategies: Mechanisms employed by essential for combating bacterial and fungal infections.
pathogens to evade or suppress pulmonary immune Recent research has highlighted the role of innate
responses lymphoid cells (ILCs) in regulating mucosal immunity and
(ii) Host defense mechanisms: Innate and adaptive tissue repair, offering new insights into their potential as
9
immune responses that protect the lungs from therapeutic targets.
infection 3.1.3. Adaptive immunity: Precision and memory
(iii) Innovative therapies: Emerging therapeutic
approaches aimed at modulating pulmonary immune The adaptive immune system provides a targeted and long-
responses, including the use of immunomodulators lasting defense against invading pathogens. T lymphocytes
and vaccines – including helper T cells such as Th1, Th2, and Th17, as well
(iv) Microbiome influence: The role of the lung microbiome as regulatory T (Treg) cells – coordinate immune responses
in shaping immune responses. that are specifically tailored to distinct pathogens. On
the other hand, B lymphocytes produce antigen-specific
3. Results antibodies that neutralize pathogens and facilitate their
clearance. Recent studies in single-cell sequencing have
3.1. The pulmonary immune system revealed significant heterogeneity within pulmonary T and

The pulmonary immune system is a complex and dynamic B-cell populations, providing new insights into their roles
network that maintains a delicate balance between defending in chronic lung diseases and vaccine-induced immunity. 10
against pathogens and preventing excessive inflammation 3.1.4. The microbiome: A double-edged sword
that could harm lung tissue. As a primary interface with the
external environment, the lungs are constantly exposed to Once considered sterile, the lung microbiome is now recognized
airborne pathogens, allergens, and environmental pollutants. as a critical modulator of pulmonary immune responses.
This constant exposure necessitates a highly specialized Commensal microbes contribute to immune homeostasis
and efficient immune response to provide protection while by competing with pathogens and modulating the immune
preserving respiratory function. This section explores system. However, dysbiosis – disruptions in the microbial
the key components of the pulmonary immune system, community – has been linked to chronic inflammatory lung
emphasizing the interplay between pathogens and immune diseases such as asthma, COPD, and pulmonary fibrosis.
defense, and highlighting recent advances in research and Innovative therapeutic approaches – including probiotics and
emerging therapeutic strategies. microbiome transplantation – are being explored to restore
microbial balance and enhance pulmonary immunity. 11,12
3.1.1. The pulmonary barrier: First line of defense
3.1.5. Immunopathology: When protection turns harmful
The respiratory epithelium, lined with ciliated cells and
mucus-producing goblet cells, serves as the first physical While the immune system is essential for protection,
and biochemical barrier against airborne pathogens. dysregulated responses can lead to immunopathology.
This epithelial layer is reinforced by antimicrobial Excessive inflammation – as observed in conditions such
peptides (AMPs), surfactant proteins, and secreted as acute respiratory distress syndrome or severe COVID-
immunoglobulins that neutralize invaders before infection 19 – can cause tissue damage and impair gas exchange.
can be established. Recent studies have highlighted the Conversely, inadequate immune responses, such as those in
crucial role of the epithelial barrier in shaping immune immunocompromised individuals, may lead to persistent
responses through the release of cytokines and chemokines, infections. Understanding the mechanisms underlying
which recruit and activate immune cells. 7,8 these immune imbalances is crucial for developing targeted
therapies that effectively modulate immune responses
3.1.2. Innate immunity: Rapid and non-specific without compromising host defense. 13,14

The innate immune system in the lungs is characterized
by its rapid response to invading pathogens. Alveolar 3.1.6. Innovative perspectives: Modulating the
macrophages – the most abundant immune cells in the immune system
airways – play a crucial role in phagocytosing pathogens Recent advancements in immunology have laid the
and clearing apoptotic cells, thereby maintaining tissue foundation for innovative strategies to enhance pulmonary
homeostasis. In addition, dendritic cells act as immune immunity. These include:

Volume 2 Issue 4 (2025) 30 doi: 10.36922/MI025100019