Immunologic mechanisms in asthma.
Level 5 - mechanism / opinion, no new human data
Narrative review of immunologic mechanisms without systematic search or primary empirical data
PubMed 31703832 · doi:10.1016/j.smim.2019.101333
What was done
This is a narrative review describing the immunopathogenesis, cellular mechanisms, and molecular endotypes of asthma. The authors summarize the roles of innate and adaptive immune cells, epithelial alarmins, and downstream inflammatory pathways across Type 2 (eosinophilic, allergic, and non-allergic) and non-Type 2 (neutrophilic, obesity-associated, and exercise-induced) asthma phenotypes.
What was found
The abstract reports no primary empirical numbers or statistical comparisons. Mechanistically, Type 2 asthma involves T helper 2 (Th2) cells, type 2 innate lymphoid cells (ILC2s), IgE-secreting B cells, and eosinophils recruited via IL-5. Non-Type 2 neutrophilic asthma is characterized as non-allergic, triggered by infections, cigarette smoke, or pollution, and mediated by IL-17 produced by Th17 cells and type 3 ILCs. Bronchial epithelial activation releases upstream cytokines including IL-33, IL-25, and TSLP.
Why it matters
Understanding asthma as a collection of distinct molecular endotypes explains heterogeneous treatment responses and provides the mechanistic rationale for targeted biologic therapies such as anti-IgE, anti-IL-5, and anti-IL-4/IL-13.
Limits
The abstract provides no primary human data, quantitative metrics, or systematic search methodology. Clinical efficacy comparisons, diagnostic cutoffs for endotypes, and sample characteristics are not reported.
Cited by
- supports There are approximately seven or eight distinct subtypes of asthma, with variations including eosinophil-predominant or neutrophil-predominant profiles.