Chapter 33, Problem 1CHI

Some pathogens invade cells; others invade tissue spaces. Explain how innate responses differ for both types of pathogens.

Summary Introduction

The capability of the body to protect against entire types of foreign materials or bodies including virus, bacteria, toxic substance that enters the body is called immunity. Immunity is categorized into two types, natural or innate or nonspecific and adaptive or acquired immunity. Innate immunity is the first line of defense against any foreign bodies including microbes, encounter by the host.

Explanation of Solution

The innate or nonspecific response differs between pathogen invading tissue spaces (intracellular) and pathogen invading cells (extracellular). The pathogen that invades cells, generally the host cells are killed through phagocytosis by leukocytes in the localized area, whether by the natural killer or NK cells, macrophages, or dendritic cells. The complement can also lyse them or mark pathogen itself. The extracellular bacteria can also be killed by lysozyme and antimicrobial peptides (defensins). 

The pathogen that invades tissue spaces is countered with inflammation. The temperature at that area is increased by the leakage of blood into tissue space by stimulating an inflammatory response and it also inhibits the growth of microbes. A fibrin clot is formed frequently, and it may also limit the invaders spreading. The intracellular pathogens can prevent the several mechanisms that performed by the extracellular pathogens. Cells which is infected in placed into an antiviral state through the release of interferon, either paracrine or autocrine. Generally, the inflammatory response is activated against both extracellular and intracellular invaders.