How does Xolair affect IgA and IgE levels?

Xolair (a medicine also called omalizumab) is used to treat allergic asthma, nasal polyps and hives. It may also be used for people with food allergies. It targets a specific part of your immune system called immunoglobulin E (IgE), but research shows that Xolair does not affect IgA levels.

What Does Xolair Do?

Xolair works by blocking IgE, a type of antibody (a tiny protein in your blood) that causes allergic reactions. Here’s how:

• It grabs onto free-floating IgE in your blood, like a key fitting into a lock.
• It stops IgE from attaching to cells that release chemicals (like histamine) that cause allergy symptoms.
• It reduces the number of “allergy sensors” (called IgE receptors) on your cells over time, making you less reactive to allergens.

Does Xolair increase or decrease IgE levels?

Xolair decreases free IgE levels in the blood within 1 hour after the first dose. The average reduction observed in studies was more than 96%. However, total IgE levels in the blood increase after the first dose because once they are attached to Xolair they clear more slowly from the body.

Even though IgE levels appear higher, the binding of Xolair to free IgE reduces the amount of free IgE available to trigger allergic reactions. After stopping Xolair, your total IgE might stay high for up to a year because these “clumps” take time to clear out of your system.

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Does Xolair Affect Other Parts of Your Immune System?

Xolair is very specific, and doesn’t appear to affect other immunoglobulins:

• IgA, IgG, IgM: These are other types of antibodies that fight infections. Studies show Xolair doesn’t change their levels.
• Even if someone has low IgA (a common immune issue), Xolair won’t make it worse.

Conclusion

Xolair demonstrates a highly selective effect on immunoglobulin levels in the body, with significant impacts on IgE but no meaningful effect on IgA or other immunoglobulin classes. This selective action is central to omalizumab's therapeutic value in treating IgE-mediated allergic conditions while minimizing broader immune system disruption.

Xolair dramatically reduces free IgE levels while paradoxically increasing total IgE measurements due to the formation of longer-lasting omalizumab-IgE complexes.

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