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HLA-DQA2 is part of the HLA class II region involved in immune recognition. It should not be treated as interchangeable with HLA-DQA1 or as a measurement of how well the immune system fights infections.

HRH1 is the gene name for Histamine Receptor H1. Learn what a specific result could mean and what to ask about it.

HRH2 is the gene name for Histamine Receptor H2. Learn what a specific result could mean and what to ask about it.

IL21 encodes a cytokine involved in regulating lymphocytes, including B-cell responses. It sits within an immune network that connects T-cell help, antibody responses and inflammatory activity.

IL23R encodes part of the receptor that receives IL-23 signals. This connects the gene to the maintenance of Th17-related immune responses, which differ from the Th2 patterns discussed in allergy.

IL6 encodes interleukin-6, a cytokine involved in immune responses and acute-phase signaling. It can appear in discussions of infection, chronic inflammation and metabolic health, with effects that depend on the context.

KIT encodes a receptor tyrosine kinase that responds to stem cell factor. It participates in blood-cell development and mast-cell biology, making the exact variant and testing context especially important.

MAOA helps break down some chemical messengers. A gene result cannot predict a mood or behavior.

MAOB encodes monoamine oxidase B, an enzyme involved in breaking down monoamine compounds, including dopamine. It does not simply build dopamine, and a DNA marker is not a neurotransmitter measurement.

MMP3 encodes matrix metalloproteinase 3, an enzyme involved in breaking down components of the extracellular matrix. Controlled remodeling is part of repair, while excess activity can accompany inflammatory tissue damage.

MTHFD1 helps move folate between forms used for different jobs in the body.

The homocysteine chapters include MTHFD1L in the wider folate-related genetic map.