- The non-specific (innate) immune system provides the first line of defense through physical and chemical barriers like skin and stomach acid, and triggers inflammation via cells like mast cells and basophils.
- If pathogens breach these barriers, the innate system activates complement proteins and natural killer (NK) cells to destroy invaders and alert other immune cells.
- Phagocytosis by cells such as neutrophils, macrophages, and dendritic cells engulfs and digests pathogens; dendritic cells then present antigens to initiate the adaptive response.
- The specific (adaptive) immune system targets particular pathogens using lymphocytes: B cells produce antibodies, while T cells directly kill infected cells or help coordinate the response.
- Antigen-presenting cells activate helper T cells (CD4+) and cytotoxic T cells (CD8+), which undergo clonal selection and expansion to create large populations of identical effector cells.
- After the infection is cleared, memory B and T cells remain to provide long-lasting immunity for faster, stronger responses upon re-exposure to the same pathogen.
Parent Tip: Review the logic above to help your child master the concept of the steps of immune response worksheet.
