What are the 5 first lines of defense?

The immune system can be divided into three basic lines of defense against pathogenic infection:

• The first line of defense against infection are the surface barriers that prevent the entry of pathogens into the body
• The second line of defense are the non-specific phagocytes and other internal mechanisms that comprise innate immunity
• The third line of defense are the specific lymphocytes that produce antibodies as part of the adaptive immune response

The Immune System: Three Lines of Defense

First Line of Defense

• The primary defence against infectious disease are the surface barriers that prevent pathogens from entering the body
• These surface barriers include intact skin (protect external boundaries) and mucous membranes (protect internal boundaries)
• Both the skin and mucous membranes release chemical secretions which restrict the growth of microbes on their surfaces
• If pathogens cannot enter the host body, they cannot disrupt normal physiological functions and cause disease

Second Line of Defense

• The second line of defence against infection are the non-specific cellular and molecular responses of the innate immune system
• These defences do not differentiate between different types of pathogen and respond the same way upon every infection
• Phagocytic leukocytes migrate to infection sites and engulf foreign bodies (dendritic cells then present antigens to lymphocytes)
• Inflammatory responses increase capillary permeability at infected sites, recruiting leukocytes but leading to localised swelling
• Antimicrobial proteins (such as cytokines and complement proteins) regulate immune activity within the body
• Fever increases body temperatures to activate heat-shock proteins and suppress microbial growth and propagation

Third Line of Defense

• The final line of defence against infection are the lymphocytes that produce antibodies to specific antigenic fragments
• Each B cell produces a specific antibody, and the body has millions of different B cells capable of detecting distinct antigens
• Helper T cells regulate B cell activation, ensuring that antibodies are only mass-produced at the appropriate times
• Both B and T cells will differentiate to form memory cells after activation, conferring long-term immunity to a particular pathogen

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The problems are exacerbated when management does not involve the board with strategic issues and important policy matters in a timely manner, or the board does not possess the knowledge to understand or question management’s view of the critical enterprise risks and exercise effective oversight. The result can be the rapid loss of enterprise value that took decades to build.

How does an organization safeguard itself against such developments? An effectively designed and implemented “lines-of-defense” framework can provide strong safeguards. The following are five essential lines of defense for managing risk:

• The tone of the organization
• Business unit management and process owners
• Independent risk management and compliance functions
• Internal assurance providers
• Board risk oversight and executive management

Essential to effective risk management, the lines-of-defense model is implicit in COSO’s recently issued internal control framework through the control environment, control activities, monitoring and other components of an internal control system. It provides assurance to the board of directors, as the elected representatives of the shareholders to see the organization’s operations on their behalf, that risks are reduced to a manageable level as dictated by the organization’s appetite for risk. Much more than “segregating incompatible duties” and “ensuring checks and balances,” the lines-of-defense model emphasizes a fundamental concept of risk management: From the boardroom to customer-facing processes, managing risk is everyone’s responsibility.

A common view of the lines-of-defense model is from the vantage point of executive management and the board of directors – that is, that there are three lines of defense.

Business unit management and process/risk owners comprise the first line, independent risk and compliance functions are the second line, and internal audit is the third line. This point of view has considerable merit. However, from the vantage point of shareholders and other external constituencies (an external stakeholder’s view), we see two additional lines of defense. A five-lines-of-defense model is depicted below.

You can read more on this topic in our Enterprise Risk Management Summary Approach Guide and by exploring these related tools on KnowledgeLeader:

Building Blocks for an Effective AML Enterprisewide Risk Assessment
Legal Spend Management Capability Maturity Model (CMM)
An Effective Way to Conduct a Risk Assessment Guide