Physiological Process in the Human Body – Immunity

Introduction

The immune system in the human body is responsible for repelling disease-causing organisms (pathogens). It is categorized into two broad classes – innate immunity (specific) and acquired immunity (non-specific). They operate together to repel microorganisms and prevent other invaders that might affect the normal functioning of the human body. Ideally, the physiological process in the human body refers to the activities and functions aimed at supporting life throughout their lifespan. There are two major arms of the human adaptive immune response, namely: humoral immunity and cell-mediated immunity. This response depends entirely on the production of proteins with particular microbial antigenic moieties. The purpose of this paper is to provide a description of a physiological process in the human body-immunity, in relation to cell-mediated immunity and humoral immunity. 

Cell-Mediated Immunity

Cell-mediated immunity refers to a classification of adaptive immune response whose existence is due to the formation of T-cells or antigen-specific effector. During the process of adaptive response, a multifarious effector T-cells is produced. They are actually responsible for the induction of effector functions and /or directly killing the infected cells.

The activation of T-cells leads to the formation of adaptive T cell-mediated immunity. On the other hand, the endogenous antigen activates the cytotoxic T cells (CD8) whose function is to kill the infected cells while the helper T cells (CD4) stimulate macrophage to destroy the endosomal pathogens. The regulatory T cells (CD25+FOXP3) regularly referred to as suppressor T cells prevent the immune response from causing any excessive damage to organs and tissues (Janeway, Travers, Walport, & Shlomchik, 2001). The memory T cells (CD62 + CCR7) keep the record of previous happenings to enable the immune system to react faster and effectively in case the offending organism or pathogen decides to return. 

Figure 2: Source: (Watson, 2014)

T cell responses are responsible for the defense against fungal infections and bacteria such as tuberculosis. They normally eliminate cancer cells and reject transplanted organs. The T Cell-mediated immunity functions by differentiating its antigen from non-self antigens (Chamorro-Ortega, 2015). These are the major histocompatibility complex molecules present in cancer cells and foreign cells, a process known as self-recognition (Fisher, n.d.). A lack of reactivity to own proteins is what called immunological tolerance. 

Figure 3: Source: (“Cell-mediated Immune Response Stock Vector – Illustration of immune, chemical: 39284952”, 2019)

Humoral Immunity

Humoral immunity, also known as antibody-mediated immune response, is a category of adaptive immune response whose formation is due to the production of antigen-specific Antibodies that usually attack an invading microbe. The process is facilitated by B-Cells in conjunction with CD4+T-cells (Janeway et al., 2001). Therefore, humoral immunity cannot take place in the absence of Cell-mediated immunity. 

Figure 4: Source: (Fisher, n.d.)

The humoral immunity results in the generation of proteins commonly called antibodies or immunoglobulins. Once the human body is exposed to an antigen or foreign material such as bacteria or virus, a humoral response is activated. The immunoglobulin surface acts as a B-cell antigen receptor (BCR) (Kim, & Bentley, (1999, September). The B-cell activation is two-phase. First, signals are transmitted from the antigen receptor on T-Cells to the interior of the cell. Secondly, the B-Cell antigen receptor delivers the antigen to intracellular sites (Slifka, Antia, Whitmire, & Ahmed, 1998; Manser, 2007). The B-Cell activation requires both B-cell and antigen-specific helper T cells interaction and binding of antigen by the B-cell receptor (Janeway et al., 2001). The helper T cell has the ability to recognize the presence of peptide fragments generated by MHC class II complexes (Galon et al., 2006). By binding CD40L on T cell to CD40, the helper T cells facilitate the interaction of other TNF-TNF-receptor. 

Figure 5: (Pandit, 2017)

Comparative chart

Effector   Cells   in   Adaptive   Immunity
	EffectorT   Cell	PathogenLocation	AntigenPresentation	Target   CellAction
CellularImmunity	TcCD8cytotoxic	Cytoplasm	Infected Cell MHC I	Infected cellapoptosis
	Th1CD4inflammatory	Macrophagevesicles	Macrophage MHC II	Macrophage activation to kill the pathogen
HumoralImmunity	Th2CD4helper	Extracellular	APCMHC II	B cell antibody production

Table 1: Source: (Decker, n.d.)

Figure 7: Source: (Pandit, 2017)

Conclusion

The purpose of this paper was to provide a description of a physiological process in the human body-immunity, in relation to cell-mediated immunity and humoral immunity. These are the two major arms of the human adaptive immune response. This response depends entirely on the production of proteins with particular microbial antigenic moieties. 

References

Chamorro-Ortega, M. (2015). Effect of maternally-derived immunity in the development of humoral immune responses to vaccination and subsequent challenge with BVDV (Doctoral dissertation).

Fisher, P. The innate and adaptive immune systems. Retrieved from http://missinglink.ucsf.edu/lm/immunology_module/prologue/objectives/obj02.html

Galon, J., Costes, A., Sanchez-Cabo, F., Kirilovsky, A., Mlecnik, B., Lagorce-Pagès, C., …&Zinzindohoué, F. (2006). Type, density, and location of immune cells within humancolorectal tumors predict clinical outcome. Science, 313(5795), 1960-1964.

Janeway, C. A., Travers, P., Walport, M., &Shlomchik, M. J. (2001). The complement systemand innate immunity. In Immunobiology: The Immune System in Health and Disease.5^th edition. Garland Science.

Kim, J., & Bentley, P. (1999, September). The human immune system and network intrusion detection. In 7th European Conference on Intelligent Techniques and Soft Computing (EUFIT’99), Aachen, Germany (pp. 1244-1252).

Manser, T. (Ed.). (2007). Specialization and complementation of humoral immune responses to infection (Vol. 319).Springer Science & Business Media.

Pandit, S. (2017). Cell-mediated Immunity Vs. Humoral Immunity: A Precise Comparison. Retrieved from https://bodytomy.com/cell-mediated-immunity-vs-humoral-immunity

Slifka, M. K., Antia, R., Whitmire, J. K., & Ahmed, R. (1998).Humoralimmunity due to long-lived plasma cells. Immunity, 8(3), 363-372.

Watson, L. (2014). Immune response. Retrieved from https://geekymedics.com/immune-response/