Various defensive mechanisms are used by the innate immune system, including complement mediated lysis, phagocytosis, NET formation, and the release of antimicrobial peptides (AMPs).

Immune disorders such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), long assumed to be caused by adaptive immunity, are now linked to innate immune system abnormalities.

The role of AMPs in developing autoimmune illnesses has emerged as a common topic in this research. In atopic dermatitis and psoriasis, the defensins and the solitary human cathelicidin, LL 37 peptide may have a role in developing these diseases.

Furthermore, in recent years, LL 37 has emerged as a possible contributor to the pathogenesis of SLE, RA, atherosclerosis, and probably other disorders.

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When it comes to modulating immunological responses, the function of the human version of LL 37, as well as its murine counterpart, MCRAMP, is examined in this paper.

What are The Functions of The LL 37 Peptide in The Pathogenesis of Autoimmune Illness?

Antimicrobial defense and inflammatory response initiation are critical functions of the innate immune system.

One of the most effective evolutionary conserved defensive mechanisms against bacterial and fungal invasions is antimicrobial peptides (AMP).

Epithelial cells and lymphocytes produce a large number of AMPS in the hundreds. LL 37 is the only member of the human cathelicidin family of antimicrobial peptides (AMPs).

Peptides that have antibacterial capabilities and immune system modifying properties have caught the scientific community’s attention.

These features may contribute to the development of autoimmune diseases.

How it functions?

KERATINOCYTES and NEUTROPHILS both have serine proteases called kallikreins, which break down the C terminus of the 18 kDa human hCAP18 protein to produce the cationic peptide LL 37, which has 37 amino acids. LL 37, unlike other antimicrobial peptides, may form aggregates in solution and lipid bilayers, making it resistant to proteolytic destruction.

It prefers to connect with negatively charged phospholipid membranes because of its positive charge.

Furthermore, during membrane contacts, it takes a mainly helical structure, segregating its hydrophobic residues.

Transmembrane holes develop, membrane penetration occurs, and bacterial lysis takes place. LL 37 protects cholesterol rich cell membranes against the peptide’s pore forming activities.

Secondary neutrophilic granules were first identified as the source of LL 37’s constitutive expression.

Macrophages, natural killer cells (NK), and epithelium from the skin, airways, ocular surface, and gut generate LL 37.

Inflammatory pathways, vitamin D, and endoplasmic reticulum stress all have a role in regulating its expression.

Researchers have shown that mCRAMP, the murine equivalent of LL 37, has primary antibacterial functions. Preventing bacterial infections in the skin requires LL 37 over mCRAMP.

Similarly, mice lacking mCRAMP are more vulnerable to urinary tract infections and colonization by pathogenic microorganisms.

The protective effects of mCRAMP and human LL 37 on the generation of inflammatory cytokines in response to Clostridium difficile toxin induced colon and ileal damage are further shown.

A surprising finding is that mCRAMP has been demonstrated to protect against influenza infection, showing that it also plays a part in the body’s antiviral defenses.

LL 37 regulates the recruitment of inflammatory cells and the phenotype of macrophages. LL 37 contains antibacterial and immunomodulatory properties.

Indeed, LL 37 has been shown to have pro and anti inflammatory properties, which the microenvironment and the underlying illness may influence.