Work in our lab has confirmed the presence of lectins in pollen of several species (Kameswara Rao et al., 1991; Sangeetaa, 1994; Kameswara Rao and Sangeetaa, 1996) and many of them are allergenic. This has implications in allergy. On one hand lectins (like ricin, the lectin of Ricinus communis) themselves may be allergens and on the other they can cause erythrocyte agglutination that would result in other complications. We have chosen the air breathing snake head fish (Channa striatus Bloch) as the model and found that lectins cause intracapillary agglutination and haemorrhage. Such an effect would complicate the diagnosis and management of allergy (Sangeetaa, 1994; Kameswara Rao and Sangeetaa, 1997).

IDENTIFICATION OF HUMAN AND ANIMAL BLOOD GROUPS

Currently, human blood groups are determined on the basis of reactivity against sera specifically developed for this purpose. In view of the differences in the specificity of lectins to cell surface carbohydrates, and the differences between the erythrocytes of different groups of human and animal blood with respect to the surface carbohydrates, lectins can be used in human and animal blood group determination. This will eliminate the technically involved process of raising antisera, and the practical difficulties associated with using them. Besides, with little training semiskilled workers can undertake the determination of blood groups, using lectins. The potential of this approach, encouraged us to undertake the formulation of a field kit for determining human and animal blood groups. Using data on lectin distribution gathered mainly by Dr N Sathyanada, and some by Dr Sathyanarayana Bhat, schedules for the identification of human blood groups and the blood of six animals have been developed (Appendices 35, 36). Although these schedules have been tested on over 250 different samples of blood, large scale field trials are required before they can be recommended for routine use.

a) HUMAN BLOOD GROUP LECTINS

Human bloood groups A, B, AB and O, come under the ABO series. The accurate determination of these four blood types is very critical for blood transfusion. In actual prctice, the concept of universal donors and acceptors is quite risky.

There are some factors of interest that emerged out of this study (Appendices 32, 34, 35). Conventionally when blood agglutinates with sera of both the A and B groups, the blood is identified as of AB group and when it does not agglutinate with either, it is determined as of O group. In our study we discovered lectins which can agglutinate the blood of group AB without agglutinating the blood of group A and/or B (Appendix 35). We also have found lectins that agglutinate blood of group O without agglutinating the blood of any other group.

The Bombay Blood group is a rare one and is confined to parts of Gujarat and Maharashtra. In blood banks it is identified with difficulty when antisera are used but some lectins (for example the seeed lectin of Ulex europeus) are useful in this regard. In our study we found that the seed lectin of Bauhinia tomentosa, besides a few other species, is useful in identifying the Bombay group of blood.

The leaf lectin of Elephantopus scaber preferentially agglutinated human B group erythrocytes. This lectin, after purification, may serve as an anti-B lectin; lectins specific to group B erythrocytes are rare (Sathyananda,1989).

There is no antiserum to distinguish human blood subgroup A1 from A2, and this is done in haematology labs only by using the seed lectin of Dolichos biflorus (horse gram), which is specific to A1. We found that the seed lectin of Phaseolus lunatus is specific to A2 and distinguishes it from A1.

b) LECTINS FOR THE IDENTIFICATION OF BLOOD OF ANIMALS

Identification of the blood of different animals species is of great forensic utility. There are factors in the blood of animals, that make the blood of each species, species specific. Cross species blood transfusion among animals would be as disastrous as transfusion between the human blood groups. There are no antisera for animal blood group determination. In many animals like the horse, sub-groups also occur within the species. Animals too have blood antigens but these are not critical for transfusion within the same species. Consequently, no antisera have been developed, to identify blood of even different animal species, which has been quite a disadvantage to forensic scientists. We found that some lectins can be used to distinguish the blood of sheep, pig, cow, rabbit, dog and chicken (Appendices 33, 34, 36). Significantly, the lectins of some species of plants, exclusively agglutinate the blood of each of these animals, enabling an unambiguous identification of their blood (Sathyananda, 1989; Sathyanarayana Bhat, 1993; Appendices 33, 34, 36). It is now necessary to amplify the scope of this study by including some more common animals in the work. One serious problem, in this regard, is the availability of the blood of different animals at the frequency required for the work.