Supporting the Body’s Secretory Immune SystemColds and flu are often treated with medications designed to reduce only the symptoms of these respiratory infections. These drugs can’t activate the body’s own immune response to fend off invading bacteria or viruses.That’s what makes probiotics different. Probiotics provide defense against the common cold and flu by activating the body’s own immune response.The immune system makes proteins called antibodies that fight bacteria, viruses, and toxins. One of the most common antibodies, called secretory IgA (immunoglobulin A), is found in mucous membranes. IgA acts as the body’s built-in security system within mucous membranes that line the nose and upper respiratory tract.24-26 When IgA levels are adequate, these antibodies can prevent cold and flu viruses from entering the body through the nasal mucous and respiratory tract.27