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Flashcards in Body's Defenses Deck (22):

Define: immune response

The immune system's response to a threat


List and briefly describe 3 important aspects of the adaptive body defense. (3)

1. Antigen- specific → recognizes and acts against particular pathogens or foreign substances
2. Systemic → immunity is not restricted to the initiated infection site
3. “Memory” → it recognizes and mounts even stronger attacks on previously encountered pathogens


Define: antigen

Any substance capable of mobilizing out immune system and provoking an immune response


What are the 2 crucial cells of the adaptive defense? (2)

1. Lymphocytes
2. Antigen-presenting cells (APCs)


Name and briefly describe the 2 major categories of lymphocytes. (2)

1. B lymphocytes (B cells) → produce antibodies and oversee humoral immunity
2. T lymphocytes (T cells) → are non-antibody producing lymphocytes


State the 3 stages in the lymphocyte process. (3)

1. Undergo maturing process (2-3 days) directed by the thymic hormones (thymosin)
2. When lymph nodes bind with recognized antigens, they complete their differentiation into fully mature T and B cells
3. Antigen-activated (mature lymphocytes) effector and memory cells circulate continuously in the blood stream and lymphoid organs of the body


Where do lymphocytes originate from?

Hemocytoblasts in the red marrow


What happens to lymphocytes which bind to self-antigens?

They are vigorously weeded out and destroyed


Are immature lymphocytes released from the marrow identical?



How do immature lymphocytes differentiate into B or T cells? (2)

1. T cells arise from the lymphocytes that migrate to the thymus
2. B cells develop immunocompetence in bone marrow


How many antigens can a single, immunocompetent lymphocyte react to?

Only the one, distinct antigen


Where do T and B cells migrate to after gaining immunocompetence?

Both T and B cells migrate to the lymph nodes and spleen (loose connective tissue) where encounters with antigens occur


What is the effect of the chemicals activated T cells release?

Activated T cells release chemicals that prod macrophages into becoming activated macrophages → they secrete bacterial chemicals


Where do macrophages and T cells go in the body?

1. Macrophages remain fixed in lymphoid organs
2. T cells circulate


What is the major role of antigen-presenting cells in immunity?

1. Engulf antigens
2. Present fragments of antigens like signals flags so that they can be recognized by T cells


What do dendritic cells act as?

Mobile sentinels


What do macrophages act as in the defensive system?



When are B lymphocytes stimulated to complete their development?

When antigens bind to their surface receptors → lymphocyte becomes primed


What do lymphocytes undergo after the binding event?

Clonal selections


What do the B cell clones become? (2)

1. Most become plasma cells
2. The rest become memory cells (which can respond at a later time)


What are later immune responses called?

Secondary humoral responses


What is active immunity?

When B cells encounter antigens and produce antibodies