The document discusses the evolution of adaptive immunity from innate immunity. It proposes that most adaptive immune molecules arose from innate molecules, with some exceptions like C3, MHC, and TdT. Adaptive molecules evolved abruptly, making it difficult to isolate their precursors. Some molecules evolved partly for immune functions while retaining other functions. B cell receptors, T cell receptors, RAG, TdT and parts of the complement system have identifiable innate precursors. MHC class II molecules evolved from molecules like DM that were involved in antigen processing. The adaptive immune system is unique to higher organisms and vertebrates.

1. Being ADAPTIVELY immune-
Where did it come from???
Sandeep
Satapathy,
Roll-10079

2. Innate Immunity
Non pathogen specific Immune
response
Immediate response
No memory of pathogenecity
Both in vertebrates and Lower
Organisms.
Adaptive Immunity
Pathogen specific
Immune response.
Delayed response .
Memory of
pathogenecity.
Only in Higher
Organisms and
Vertebrates.

3. Hypothesis:
Result
s
Where did the
adaptive molecules
come from?
How spontaneous
is this evolution?
Were there any
precursor cells,which
were initially non-
immune cells?
Mostly the adaptive
immune molecules arose
from the innate molecules
with few exception like
C3,MHC,TdT.
Adaptive molecules evolved
abruptly and isolating their
precursors is tedious.
Molecules with different
alias/function evolved
partly to be immune
molecules while other
retained their identity.

4. Adaptive molecules/Cells
B Cell Receptors (Ig)
T Cell Receptors(TCR)
Major Histocompatibility
Complex (MHC)
Recombination activation
Gene(RAG)
Terminal dinucleotide
transferases(TdT)
Complement
System
C3,Factor B,Factor
D-Alternative CS-
Innate
MASP-Lectin CS-
Innate
C1,C4,C2-Classical-
Adaptive
Innate Immune System-
Macrophages, NK cells, Nuetrophils,Eosinophils,
Dendritic Cells

5. Ig(BCR) and TCR Evolution:
Ig and TCRs(have high structural
similarity)- belong to the Ig
superfamily.
RAGS and TdTs- accommodate variability in these
lymphocytic receptors- maximise antigenic determinants
recognition.
Direct ancestors of Igs and TCRs were similar to the Ig
superfamily of NK cells in mammals- Innate precursors
in higher organisms.
Also precursors were similar to Ig superfamily of NITR
family found in invertebrates and bony fish-Innate
precursors in lower organisms.

6. Horizontal Gene
Transfer
Precursor
of RAG RAG-1&2
Precursor
of TdT
TdTs
No distinct immune
Function
Distinct
lymphocytic
receptor
recombination

7. MHC Evolution: A short evolutionary dwell
Many diverse group of molecules (classical and non
classical) with both innate and adaptive immune
functions.
These molecules dwindle for different functions
in very short evolutionary timescale.
MHC Class II molecules evolved first from
precursors, like DM genes .
Precursor of MHC II
e.g DM
Involved in antigen
processing
MHC II
Mainly act as chaperons
for antigen presentation.

8. Complement Cascade
Evolution:
Adaptive
Innate
Non-immune precursors
(Alpha-2-Macroglobulin-
serine protease inhibitor)
(Alternative
CS)
(Classical CS)
Lectin
CS

9. Conclusion:
Innate Immune molecules
Non-immune cells
Adaptive Immune system
molecules
Dragged force Evolution with few
functionally divergent evolution and
other function and pattern retaining
conserved evolution.
Co-evolution with higher structural
similarity and functional polymorphism.Freque
nt
Rar
e
Both in Lower and higher
organisms.
Only vertebrates and higher
organisms.

10. Thank you
all..........