Your immune system is fighting on half-strength. Your genes may be why.

HLA-DQ2 is part of your major histocompatibility complex, the system that displays foreign antigens to your immune cells so they can decide whether to attack. Your HLA type is like the security system that determines which threats your T-cells can recognize and respond to. Different HLA variants recognize different sets of pathogens, and different sets of self-proteins that might trigger autoimmunity.

Approximately 25 to 30 percent of people with European ancestry carry HLA-DQ2. If you have this variant, your immune system is primed to recognize certain bacterial and viral patterns, but also certain proteins in gluten, dairy, and other common foods. This doesn’t mean you have celiac disease or food intolerance, but it does mean your immune system is genetically predisposed to treat these molecules as threats. It also increases your baseline risk for type 1 diabetes and other autoimmune conditions.

You might notice you’re unusually sensitive to certain foods, or that you have lingering digestive issues even though testing for celiac came back negative. You might struggle with skin conditions, joint inflammation, or a sense that your immune system is always slightly activated. These aren’t failures of willpower; they’re the predictable outcome of your immune cells being trained to recognize threat patterns that most people don’t react to.

CTLA4 is a checkpoint protein on the surface of T-cells. Its job is to act as a brake. When an immune response has done its job, CTLA4 receives a signal and tells the T-cell to disengage, stop proliferating, and wind down the inflammatory attack. Without a functional CTLA4 checkpoint, T-cells keep firing even after the threat is neutralized. This is why CTLA4 dysfunction is central to autoimmune disease.

Roughly 45 percent of the population carries the +49A>G variant in CTLA4. This variant reduces the efficiency of the CTLA4 brake, allowing T-cells to remain activated longer than they should. Your immune system doesn’t turn off cleanly. It lingers in a state of partial activation, which triggers chronic inflammation and increases your risk of autoimmune flares.

You might notice that after you get sick, you don’t fully recover. Your energy stays low, your inflammation markers stay elevated, and minor infections linger. You might develop joint pain, skin rashes, or other autoimmune symptoms that appear and disappear unpredictably. This is what happens when your immune off-switch isn’t working properly.

TLR4, toll-like receptor 4, is one of your innate immune system’s primary sensors for gram-negative bacteria. When bacteria release endotoxin (lipopolysaccharide, or LPS), TLR4 recognizes it and triggers an immediate inflammatory response. This is your body’s emergency alarm system. A functional TLR4 means you can mount a rapid defense against bacterial infection. A dysfunctional TLR4 means you’re slower to respond.

The TLR4 D299G variant is carried by roughly 10 percent of people with European ancestry. This variant reduces your TLR4’s ability to recognize and bind endotoxin, which impairs your early bacterial immune response. You can’t sense the threat as quickly or as clearly, so your innate immune system is slower to mobilize. This makes you more vulnerable to certain bacterial infections, and it can allow bacteria to establish themselves more deeply in your system before you mount a strong defense.

If you carry this variant, you might notice you’re slower to feel the onset of infection, or that bacterial infections take longer to clear even with antibiotics. You might get recurrent sinus infections, urinary tract infections, or respiratory infections that don’t respond as quickly as they should. Your body is fighting with a broken early-warning system.

TNF, tumor necrosis factor-alpha, is one of your immune system’s most powerful inflammatory signaling molecules. When you get an infection or sustain an injury, your immune cells release TNF to signal the rest of your system that there’s a threat and to activate inflammation. TNF is essential for fighting infections, but if it’s produced in excessive amounts, it drives chronic systemic inflammation that damages your own tissues.

The TNF -308G>A variant is carried by approximately 30 percent of people with European ancestry. The A allele pushes your TNF production higher, meaning your immune system triggers stronger inflammatory signals for any given threat. You produce more TNF per infection, more TNF per injury, and you maintain elevated TNF levels even between infections. Your inflammatory baseline is simply higher than average.

You might feel like you’re always running a low-grade fever, or that every minor infection becomes a major ordeal. You might experience joint pain, muscle soreness, or fatigue that seems disproportionate to the actual threat. Your body is responding to normal challenges with an oversized inflammatory hammer.

IL6, interleukin-6, is an inflammatory cytokine that amplifies whatever immune response is already in motion. When TNF or other signals tell your immune system to activate, IL6 spreads that message systemically and sustains the inflammatory state. IL6 is also a key driver of neuroinflammation, which means it crosses the blood-brain barrier and triggers inflammation inside your brain. Elevated IL6 is associated with brain fog, fatigue, and depression.

Roughly 40 percent of the population carries the -174G>C variant in the IL6 promoter. The C allele increases IL6 production, which means your immune system generates stronger and longer-lasting inflammatory signals. Your inflammation doesn’t come in brief spikes; it simmers at a higher baseline and can cascade into systemic activation more easily.

You might experience persistent fatigue even when you’re not actively fighting an infection. You might have brain fog, difficulty concentrating, or mood changes that correlate with your infection history or stress levels. Your immune system is broadcasting a constant low-volume inflammatory message that reaches your brain.

FUT2, fucosyltransferase 2, catalyzes the addition of fucose residues to glycans on your epithelial cells, especially in your gut and respiratory tract. These glycan structures serve as binding sites for your gut microbiota. They help determine which bacterial species can colonize your system and which cannot. FUT2 essentially writes the chemical language that your microbiota reads. Your microbiota composition directly determines the strength and balance of your immune system.

Approximately 50 percent of the population carries a less-active FUT2 variant (rs601338). This variant shifts your gut microbial composition toward species that are less effective at training and regulating your immune system. You lose beneficial bacteria that produce short-chain fatty acids and bacterial lipopolysaccharides that activate immune regulation. You become more susceptible to pathogenic colonization and less able to mount appropriate immune tolerance.

You might experience recurrent gastrointestinal infections, or you might have a gut microbiota that never seems stable no matter what you eat. You might struggle with food sensitivities or a leaky gut feeling. Your immune system isn’t getting the microbial signals it needs to calibrate properly.