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- Presentation
Core Immunology: Innate and Adaptive Immune Responses in Skin Disease
Description
The talk reviews core immunology in skin disease, contrasting the rapid, nonspecific innate immune response with the slower, specific adaptive response that has memory. In the skin, dendritic cells, especially Langerhans cells, act as a bridge through the immunologic synapse, while MHC class I and II help present self and antigen; loss of immune privilege can expose tissues such as hair follicles to immune attack, contributing to alopecia areata. The speaker explains pattern-recognition pathways including toll-like receptors, nod-like receptors, inflammasome, and complement, and links them to diseases such as acne, rosacea, actinic keratosis, and atopic dermatitis. A major theme is how different cytokine patterns map to disease: type 2 cytokines like IL-4, IL-13, IL-5, and IL-31 drive eczema and barrier dysfunction; type 3 cytokines like IL-23 and IL-17 drive psoriasis; and IL-36 is especially important in generalized pustular psoriasis, where neutrophils dominate. Counter-regulation is emphasized through IL-10, TGF-beta, and Tregs, showing that immune pathways are balanced and often suppress one another. Clinical examples include IL-17 blockade leading to candidiasis risk, reflecting IL-17’s role in antimicrobial defense, and the use of biologics, small molecules, and newer oral small peptides to target specific pathways. The lecture ends with hidradenitis suppurativa as a mixed innate-adaptive disorder, where combined IL-17A/F blockade can produce stronger benefit by addressing both arms of the immune response.
View moreConclusions
- Cutaneous immune diseases are driven by distinct but overlapping innate and adaptive pathways, with the dominant cytokine program helping explain disease behavior and treatment response.
- The innate immune system provides rapid, nonspecific skin defense through PRRs, antimicrobial peptides, NK cells, and inflammatory mediators, and its dysregulation contributes to conditions such as acne, rosacea, atopic dermatitis, psoriasis, and alopecia areata.
- Immune privilege in sites like the anagen hair follicle normally limits immune attack, and loss of this privilege with increased MHC expression is likely an early event in alopecia areata.
- Plaque psoriasis is primarily a type 3/adaptive disease driven by the IL-23/IL-17 axis, but it still contains important innate signatures such as neutrophils and antimicrobial peptides.
- Generalized pustular psoriasis is mechanistically distinct from plaque psoriasis and is more dependent on innate immunity, especially the IL-36 pathway and neutrophil recruitment.
- Atopic dermatitis reflects barrier dysfunction that promotes type 2 inflammation and reduces antimicrobial protection, which explains its greater susceptibility to bacterial and viral infections.
- Counter-regulatory cytokines and Treg-associated mediators such as IL-10 and TGF-beta help restrain immune responses and shape which inflammatory pathway predominates.
- Targeted therapies work best when they match the dominant immune pathway, which is why IL-23/IL-17 blockade helps plaque psoriasis but is less effective for IL-36-driven pustular disease.
- Blocking IL-17 can predispose to candidiasis because IL-17 is important for mucocutaneous antifungal defense and antimicrobial peptide induction.
- Complex mixed disorders such as hidradenitis suppurativa likely require therapies that address both innate and adaptive inflammation, and dual IL-17A/F blockade may provide stronger benefit than targeting either alone.
- New therapeutic modalities are expanding options: biologics are highly specific but cannot enter cells, small molecules can enter cells but are less specific, and small peptides may combine specificity with oral delivery and intracellular access.
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