Cathelicidin Antimicrobial Peptide
Family

The Discovery

The Puzzle Begins

Strange Peptides in Cow Blood

In the 1980s, researchers studied white blood cells from cows and discovered something odd. Different antimicrobial peptides seemed to come from the same cell type but looked completely unrelated. Scientists named them Bac5, Bac7, and Lf-B30.

Each one could kill bacteria. But they seemed like separate discoveries. No one realized they were cousins in one big family. It was like finding different tools in a toolbox but not recognizing they all came from the same company.

The mystery deepened. Why did cows produce so many different antimicrobial peptides? What connected them? Scientists were puzzled.

The Breakthrough

The Breakthrough

A Hidden Connection Found

In 1989, scientist Ranieri Ritonja discovered a pig protein called cathelin. It was inside larger precursor proteins. Then Gennaro Romeo's team realized something incredible.

All those strange cow peptides shared the same structure as cathelin! They all started with a cathelin-like section attached to a unique antimicrobial part. The pieces clicked together. These weren't separate peptides. They were all the same family.

It was like recognizing that different model cars all came from the same factory. The frame was the same (cathelin), but the engines were different. Romeo's team published their findings. Other scientists started looking at animals everywhere.

The Trials

Giving the Family a Name

The Cathelicidin Family is Born

Margherita Zanetti and her colleagues coined the term cathelicidin in 1995. They said, 'We should call this entire family cathelicidins because they all have cathelin-like domains.'

Scientists looked everywhere. Pigs had PR-39 and protegrins. Cattle had BMAP-27 and BMAP-28. Humans had LL-37. Mice had CRAMP. Fish had their own versions. Even chickens and frogs had cathelicidins. Every animal studied had at least one.

Each was shaped differently but built on the same blueprint. It was one of the biggest discoveries in immunology. A whole family had been hiding in plain sight all along.

The Crisis

Decoding the Secret

How They Work

Scientists discovered cathelicidins work like tiny arrows made of amino acids. The cathelin domain was just packaging. When white blood cells released these peptides, special scissors (proteases) cut off the cathelin part.

This left the sharp antimicrobial blade. The blade punched holes in bacterial cell membranes. Some cathelicidins like PR-39 from pigs worked differently. They snuck inside bacteria and stopped them from making new DNA. By 2000, researchers realized cathelicidins also talked to vitamin D.

Together they fought tuberculosis and serious infections. Scientists in 2007 proved that vitamin D directly increases cathelicidin production. This explained why sun-exposed populations have fewer TB infections.

The Legacy

From Laboratory to Clinic

Future Battles Ahead

Today, cathelicidin research has exploded. Scientists test them against antibiotic-resistant superbugs. Human LL-37 entered clinical trials in 2020 for wound healing and infection control. Drug companies engineer enhanced versions based on pig PR-39 and other animal models.

Some see cathelicidins as humanity's ancient immune software. This system has been in every creature for millions of years. It's waiting to be weaponized against modern threats like resistant bacteria. The family that seemed like separate discoveries now looks like evolution's greatest gift to survival.

Future treatments may include topical creams for acne and eczema. Inhalable versions could fight lung infections. Genetic testing might reveal which cathelicidins each person produces best.