Immunity refers to the body's ability to resist or eliminate potentially harmful foreign materials or abnormal cells, and it is divided into two main types: innate immunity and adaptive immunity.

1. Innate Immunity: This is the first line of defense and is non-specific, meaning it doesn't target specific pathogens. It includes physical barriers like skin and mucous membranes, and internal defenses like phagocytes, natural killer cells, inflammation, and fever. Innate immunity is present at birth.

2. Adaptive Immunity: This is the second line of defense and is specific, meaning it targets specific pathogens. It is not present at birth but is acquired over a lifetime. Adaptive immunity has two branches: humoral immunity and cell-mediated immunity.

a. Humoral Immunity: This involves B cells that produce antibodies in response to antigens or pathogens circulating in the lymph or blood. The antibodies then neutralize, eliminate, or prevent the spread of the pathogen.

b. Cell-Mediated Immunity: This involves T cells and responds to any cell that displays aberrant MHC markers, including cells invaded by pathogens, tumor cells, or transplanted cells.

In addition to innate and adaptive immunity, there is also passive and active immunity:

1. Passive Immunity: This type of immunity is "borrowed" from another source and it lasts for a short time. For example, a baby receiving antibodies from the mother through the placenta before birth or through breast milk after birth.

2. Active Immunity: This type of immunity is created by the person's own immune system. This happens either after getting a disease and recovering or after receiving a vaccine.

Question

Immunity refers to the body's ability to resist or eliminate potentially harmful foreign materials or abnormal cells, and it is divided into two main types: innate immunity and adaptive immunity.

1. Innate Immunity: This is the first line of defense and is non-specific, meaning it doesn't target specific pathogens. It includes physical barriers like skin and mucous membranes, and internal defenses like phagocytes, natural killer cells, inflammation, and fever. Innate immunity is present at birth.

2. Adaptive Immunity: This is the second line of defense and is specific, meaning it targets specific pathogens. It is not present at birth but is acquired over a lifetime. Adaptive immunity has two branches: humoral immunity and cell-mediated immunity.

a. Humoral Immunity: This involves B cells that produce antibodies in response to antigens or pathogens circulating in the lymph or blood. The antibodies then neutralize, eliminate, or prevent the spread of the pathogen.

b. Cell-Mediated Immunity: This involves T cells and responds to any cell that displays aberrant MHC markers, including cells invaded by pathogens, tumor cells, or transplanted cells.

In addition to innate and adaptive immunity, there is also passive and active immunity:

1. Passive Immunity: This type of immunity is "borrowed" from another source and it lasts for a short time. For example, a baby receiving antibodies from the mother through the placenta before birth or through breast milk after birth.

2. Active Immunity: This type of immunity is created by the person's own immune system. This happens either after getting a disease and recovering or after receiving a vaccine.

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