Intimate Ennemies

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By Marcel Pouchelet

Narration

The events that are about to be displayed before your eyes are the latest reports from a war that started several thousands years ago.

1
THE OPPONENTS

MACROPHAGES
In every organism, including humans, are macrophages. They are very mobile cells specialized in policing the environment against intruders.

There are two ways to observe them under a microscope:
In one case we get the impression of a surfacing light which provides an illusion of a mountainous relief.
In the other case the light provides an impression of perfect transparency.

However they appear to our eyes, that does not change their basic behaviour.

Cultivated macrophages, that is to say macrophages that have been isolated and transferred into an appropriate nourishing milieu, lose a few microns of freedom but gain in visibility.

LEISHMANIES
Leishmanies are parasites. While hosted by the sand fly, the leishmanies are spindle shaped and move fast with the help of a tail (flagelle). Then they shape into promastigotes. When they are hosted in an individual, human for instance, they lose their mobility and are then called amastigotes.

The unequal size of the fighters – the macrophage is almost fifty times the size of a leishmanie – might let one presume how this battle is going to unfold.

But let's not sell the leishmanies short.

2
THE GIANT

As all cells are, the macrophage is an autonomous drop of life bound by an extremely mobile and yielding membrane that endlessly explores the environment around itself. This membrane divides an interior rich in life with an exterior rich in nourishment… and dangers.

To feed itself, the macrophage drains a small amount of liquid from the outside, thanks to the marvelously flexible movements of the edge of its membrane. Inside the fine-grained cell organism, the liquid shapes into transparent discs.

Those transparent discs - small chunks of food - can merge into bigger ones, and are incorporated little by little by the cell.

The edge of the membrane, busy absorbing the food outside, can also capture foreign bodies passing by.

One can hardly imagine the richness of that drop of life called a cell.

The leishmanie is hosted by the sandfly… the macrophage by humans…
A bite of a fly barely separates the two.

3
THE WAR

The leishmanies encounter the macrophages.

As soon as a parasite touches a macrophage, the edge of the membrane grabs it and pulls it inside the cell.

How, and why, does the macrophage capture the parasite? Hazard or choice ? No one can tell.

Either the parasite touches the macrophage and it is captured or a border of the membrane pulls toward the parasite.

The macrophage, in a tireless rapture, grabs at any parasite passing by, mechanically, remorselessly, the giant swallows Liliput… But is the macrophage a hunter, or merely a passive beneficiary?

Some evidence seems to show that there could be choice.  Some evidence seems to show that there could be collaboration.

The parasites passed from the outside of the macrophage – a wild and unstable environment – to the inside, which is dangerous but structured and therefore predictable.  

Maybe the leishmanies do not lose in this situation.

4
IN CAMERA

The leishmanies have now become completely engulfed and absorbed by the macrophage. A phenomenon known as phagoctyose. This is the first phase of the battle. There are no more parasites left in the environment.

The new terrain where the intimate enemies square off is inside the macrophage itself.

In the macrophages, the leishmanies should be digested and crushed.
But they survive… by tactic or complicity between the intimate enemies ?

Around the parasite, a clear space opens up, called a vacuole parasitophore… the suffix "phore" meaning "to carry".

In these vacuoles, the leishmanies sometimes waltz.

Why do the leishmanies act like a whirling dervish ? This is another mystery.

In the vacuoles, the parasite can divide itself, that is to say reproduce. This has been suspected to happen for sometime, but no one has actually seen it. Until this image you are watching right now.

Some vacuoles parasitophores can merge. The big vacuoles are formed that way with several parasites.

In that group of macrophages, filmed during 72 hours, the vacuoles parasitophores get bigger, merge with one another and deform the cells. The macrophages turn out misshapen, distorted by the huge vacuoles parasitophores.

They are unrecognizable.

5
ARMED PEACE

In the macrophages, the vacuoles carrying the leishmanies grow bigger and deform the cells.

Among the distorted macrophages some die out … the membrane cracks open and the parasites find themselves in the outside milieu. A neighboring macrophage phagocytes the loose leishmanies.

Or, it can happen that the leishmanies, loosened after the death of a macrophage, do not get phagocyted by another macrophage.

The state of armed peace is complex… Why do the parasites pass from one macrophage to another? Is the leishmanie that crosses the membrane or is it the macrophage that gives her up… or takes.

What are the strange conversations, and the strange negotiations that result in those transfers?

A lot remains to be known, a lot remains to be understood, and learned.

The leishmanises are disabling illnesses that can lead to death. During that war that is as old as life, neither the macrophages nor the leishmanies have extinguished their resource. Nowadays the macrophages synthesize the toxic substances and on their side the leishmanies develop new strategies to shorten the production of those substances. Humans, on their side, nourish molecules that help… the macrophages.