Artificial Immune Systems

1. BY: Nazanin Asadi ZohreMolaei Artificial Immune Systems Isfahan University of Technology

2. Outline History Natural Immune System Artificial Immune System Application Experiment Result Reference

3. History • Developed from the field of theoretical immunology in the mid 1980’s. • 1990 – Bersini first use of immune algorithms to solve problems • Forrest et al – Computer Security mid 1990’s • Hunt et al, mid 1990’s – Machine learning

4. Basic Immunology

5. Role of the Immune System • Protect our bodies from infection • Primary immune response • Launch a response to invading pathogens • Secondary immune response • Remember past encounters • Faster response the second time around • The IS is adaptable (presents learning and memory)

6. Where is it ?

7. Lymphocytes • Carry antigen receptors that are specific • They are produced in the bone marrow through random re-arrangement • B and T Cells are the main actors of the adaptive immune system

8. B Cell Pattern Recognition • B cells have receptors called antibodies • The immune recognition is based on the complementarity between the binding region of the receptor and a portion of the antigen called the epitope. • Recognition is not just by a single antibody, but a collection of them • Learn not through a single agent, but multiple ones

9. T-cells • Regulation of other cells • Active in the immune response • Helper T-cells • Killer T-cells

10. Immune Responses

11. The Immune System models The are many different viewpoints These views are not mutually exclusive

12. Artificial Immune Systems

13. Basic concepts • trained detectors(artificial lymphocytes) that detect nonself patterns • need a good repository of self patterns or self and non-self patterns to train ALCs to be self tolerant • need to measure the affinity between an ALC and a pattern • To be able to measure affinity, the representation of the patterns and the ALCs need to have the same structure • The affinity between two ALCs needs to be measured • memory that frequently detect non-self patterns • When an ALC detects non-self patterns, it can be cloned and the clones can be mutated to have more diversity in the search space

14. AIS Framework Solution Algorithms Shape-Space Binary Integer Real-valued Symbolic Affinity AIS Representation Application

15. Representation – Shape Space • Used for modeling antibody and antigen • Determine a measure to calculate affinity • Hamming shape space(binary) • 1 if Abi != Agi: 0 otherwise (XOR operator)

16. Representation • Assume the general case: • Ab = Ab1, Ab2, ..., AbL • Ag = Ag1, Ag2, ..., AgL • Binary representation • Matching by bits • Continuous (numeric) • Real or Integer, typically Euclidian • Symbolic (Categorical /nominal) • E.g female or male of the attribute Gender.

17. AIS Framework Solution Algorithms Euclidean Manhattan Hamming Affinity AIS Representation Application

18. Affinity • Euclidean • Manhattan • Hamming

19. AIS Framework Solution Bone Marrow Models Negative Selection Clonal Selection Positive Selection Immune Network Models Algorithms Affinity AIS Representation Application

20. Basic AIS Algorithm

21. Negative Selection Algorithms • Forrest 1994: Idea taken from the negative selection of T-cells in the thymus • Applied initially to computer security • Split into two parts: • Censoring • Monitoring

22. All patterns and ALCs : as nominal valued attributes or as binary strings • Affinity : r-continuous matching rule • Training set : self patterns

23. Training ALCs with negative selection

24. Clonal Selection

25. Clonal Selection • selection of a set of ALCs with the highest calculated affinity with a non-self pattern • cloned and mutated • compete with the existing set of ALCs • to be exposed to the next non-self pattern Continuous (numeric)

26. ClONALG algorithm • De Castro and Von presented CLONALG as an algorithm,2001 • initially proposed to perform • machine-learning • pattern recognition • Adapted to be applied to optimization problem

27. ClONALG algorithm • main immune aspects taken into account to develop the algorithm • maintenance of a specific memory set • selection and cloning of the most stimulated Antibodies • death of non-stimulated antibodies • affinity maturation and re-selection of the clones proportionally to their antigenic affinity • generation and maintenance of diversity

28. ClONALG • All patterns in binary strings • Training set : non-self patterns • Affinity : Hamming distance , between ALC and non-self pattern • Lower Hamming distance = stronger affinity • Assumption : One memory ALC for each of the patterns that needs to be recognized in training set

29. ClONALG

30. CLONALG optimization case • an objective function g(⋅) must to be optimized (maximized or minimized) • antibody affinity corresponds to the objective function • each antibody Abi represents an element of the input space • it is no longer necessary to maintain a separate memory set Ab

31. CLONALG optimization case

32. CLONALG optimization case

33. Immune Network Models • The ALCs interact with each other to learn the structure of a non-self pattern • The ALCs in a network co-stimulates and/or co-suppress each other to adapt to the non-self pattern • The stimulation of an ALC • based on the calculated affinity between the ALC and the non-self pattern • the calculated affinity between the ALC and network ALCs as co-stimulation and/or co-suppression.

34. Artificial Immune Network • Timmis and Neal,2000 • Application • clustering • data visualization • control • optimization domains • AINE defines the new concept of artificial recognition balls (ARBs) • population of ARBs • links between the ARBs • a set of antigen training patterns • Some clonal operations for learning

35. Artificial Immune Network

36. Artificial Immune Network • all training patterns in set DT are presented to the set of ARBs • After each iteration, each ARB • calculates its stimulation level • Allocates resources (i.e. B-Cells) based on its stimulation level as • The stimulation level • antigen stimulation • network stimulation • network suppression

37. Artificial Immune Network

38. Stimulation level

39. Resource allocation

40. Danger Theory Models • distinguishes between what is dangerous and non-dangerous • Include a signal to determine whether a non-self pattern is dangerous or not

41. An Adaptive Mailbox • classifies interesting from uninteresting emails • initialization phase (training) • running phase (testing)

42. initialization phase

43. running phase

44. Application of AIS • network intrusion and anomaly detection • data classification models • virus detection • concept learning • data clustering • robotics • pattern recognition and data mining • optimization of multi-modal functions

45. PSO and AIS

46. PSO and AIS • PSO performs about 56 percent faster than. • AIS performs faster than PSO (about 14 percent) for simpler mathematical functions

47. Reference • Computational Intelligence An introduction , AdndriesP.Engelbrecht • Learning and Optimization Using the Clonal Selection Principle, Leandro N. de Castro, ,Fernando J. Von Zuben, IEEE,2002 • A Comparative Analysis on the Performance of Particle Swarm Optimization and Artificial Immune Systems for Mathematical Test Functions, 1David F.W. Yap, 2S.P. Koh, 2S.K. Tiong,Australian Journal of Basic and Applied Sciences, 2009