Binary (secondary) exposure to an antigen results in sudden increase in ?
**Core Concept**
Binary (secondary) exposure to an antigen occurs when an individual is re-exposed to the same antigen they were previously sensitized to. This exposure triggers a pre-existing immune response, leading to a rapid increase in the production of antibodies and immune cells.
**Why the Correct Answer is Right**
During binary exposure, the previously formed antibodies recognize the antigen and bind to it, marking it for destruction. This process activates the complement system, leading to the formation of a membrane attack complex (MAC) that creates pores in the target cell's membrane, causing cell lysis. Additionally, the pre-formed memory T cells are rapidly activated, releasing cytokines that enhance the immune response.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because primary exposure to an antigen does not result in a sudden increase in antibodies and immune cells, as the body has not yet formed a memory response.
**Option B:** This option is incorrect because tertiary exposure to an antigen occurs when an individual is exposed to a different antigen, triggering a new immune response, not a sudden increase in pre-existing antibodies and immune cells.
**Option D:** This option is incorrect because tolerance occurs when the immune system fails to respond to an antigen, often due to a lack of exposure or a regulatory mechanism suppressing the immune response, not a sudden increase in antibodies and immune cells.
**Clinical Pearl / High-Yield Fact**
When a patient experiences a sudden increase in antibodies and immune cells due to binary exposure, it can lead to anaphylaxis, a severe and life-threatening allergic reaction. Clinicians must be aware of this possibility and take prompt action to manage the patient's symptoms.
**Correct Answer: C. Anaphylaxis**