Immunology concept check: In human immunity, the absence of an immune response to our own human leukocyte antigens (HLAs) is termed what?

Introduction / Context:
Self–nonself discrimination is a cornerstone of immunology. The immune system must react strongly to pathogens while remaining quiescent toward the body’s own molecules, including human leukocyte antigens (HLAs). The regulated lack of response to self is known as immune tolerance and prevents autoimmune disease.

Given Data / Assumptions:

• HLAs are the human form of major histocompatibility complex molecules and are expressed on most cells.
• Question asks for the term describing lack of reaction to one’s own HLAs.
• We consider foundational immunology definitions used in clinical and exam settings.

Concept / Approach:
Immune tolerance includes central tolerance (in thymus for T cells and bone marrow for B cells) and peripheral tolerance (anergy, suppression by regulatory T cells, and deletion in the periphery). Together these mechanisms silence or delete self-reactive lymphocytes so they do not attack cells displaying self-HLA plus self-peptide.

Step-by-Step Solution:

Verification / Alternative check:
Clinically, breakdowns in tolerance lead to autoimmune conditions (e.g., type 1 diabetes, SLE). Experimental assays show deletion of strongly self-reactive T-cell clones during thymic selection, evidencing central tolerance.

Why Other Options Are Wrong:

• Autoimmunity: the opposite state—immune attack against self antigens.
• Complement system: a set of innate serum proteins, not a tolerance mechanism.
• Clonal selection: principle explaining expansion of antigen-specific lymphocytes, not their non-responsiveness to self.

Common Pitfalls:
Confusing “tolerance” with “immunodeficiency.” Tolerance is a targeted lack of response to self, whereas immunodeficiency is a broad failure to respond to pathogens.

Final Answer:
tolerance