2.Risk factors


*Reactive Oxygen Species in the Development and Resolution of Autoimmune and Inflammatory… DOI: http://dx.doi.org/10.5772/intechopen.99988*

subgroups and races have been associated with having a relatively high frequency of autoimmune diseases risk alleles. However, genetic risk factors only confer a small risk and can only explain a limited proportion of heritability in relation to autoimmune diseases [30]. Investigated population and additive and non-additive factors should be considered when assessing heritability in autoimmunity.


#### **Figure 1.**

*Development of autoimmune disease. Following the generation and maturation of immune cells in the bone marrow and thymus, the cells undergo a series of processes to produce immuno tolerant cells. A small number of T and B cells evade this process and form autoreactive T and B cells. However these cells are harmless until acted upon by genetic or environmental factors autoantibody can trigger autoimmunity for long term.*

patient [33]. This can increase the challenge in acquiring a better understanding of autoimmune diseases because although subphenotypes are similar, they can change depending on the diseases activity and duration [34].

4.Recurrence risk: Complex diseases such as autoimmune diseases tend to cause phenotype clusters in the family of the infected individual. This aggregation usually occurs in a higher frequency than what is observed in the general population [29]. The presence of different autoimmune diseases in the members of the nuclear family is known as familial autoimmunity. When a specific autoimmune disease occurs in the family, it is known as familial autoimmune diseases [18]. Familial autoimmunity is common than a familial autoimmune disease (**Figure 1**).
