How to tell if you have a weak or strong immune system

WHEN you are under the covers, sniffling from your third cold of the year, you might wonder whether your immune system is pulling its weight. It is a question we would all love to answer: is our immune system healthy or not? Now, a burgeoning field of immunology is attempting to do just that with tests that “grade” your immune system, the idea being that it could help people preempt problems and motivate them to make lifestyle changes to avoid ill health.

To understand how healthy your immune system really is, let alone improve it, first it is helpful to get to grips with what it actually does. Consider it your internal army, with different units coordinating to eliminate enemy invaders, all while avoiding collateral damage to your own tissues and constantly adapting to new challenges.

Like a real army, your immune system can also fall into disarray, with some units underperforming while others go rogue. This can cause major illnesses.

So how do you tell whether your army is doing its best? Let’s begin by considering the different components. The first line of defence comes from innate immune cells such as macrophages, which engulf bacteria and release chemicals that trigger inflammation, making cells less hospitable to pathogens.

Once a threat has been identified, a second line of defence called the adaptive immune system kicks in, with more specialised tools. B-cells, for example, form antibodies that bind to the unwanted newcomer and render it harmless. T-cells, meanwhile, include killer cells…